add day 10 code

Makefile.common.mk

@@ -0,0 +1,54 @@
+CC := clang
+YACC := bison
+LEX := flex
+CFLAGS := -std=c17 -Wpedantic -Wall -Wextra
+BISONFLAGS := 
+BUILD := ./build
+INCLUDE	:= -I./
+OBJ_DIR := $(BUILD)/objects
+APP_DIR := $(BUILD)/bin
+
+SRC := $(wildcard ./*.c) lexer.c parser.c
+OBJECTS	:= $(SRC:%.c=$(OBJ_DIR)/%.o)
+
+# targets
+all: build $(APP_DIR)/$(TARGET)
+
+run: all
+	$(APP_DIR)/$(TARGET)
+
+flex:
+	$(LEX) --outfile=lexer.c --header-file=lexer.h lexer.l
+
+bison:
+	$(YACC) $(BISONFLAGS) --output=parser.c parser.y
+
+generate: flex bison
+
+$(OBJ_DIR)/%.o: %.c
+	@mkdir -p $(@D)
+	$(CC) $(CFLAGS) $(INCLUDE) -o $@ -c $<
+
+$(APP_DIR)/$(TARGET): flex bison $(OBJECTS)
+	@mkdir -p $(@D)
+	$(CC) $(CFLAGS) $(INCLUDE) $(LDFLAGS) -o $(APP_DIR)/$(TARGET) $(OBJECTS)
+
+.PHONY: all build clean debug release
+
+build:
+	@mkdir -p $(APP_DIR)
+	@mkdir -p $(OBJ_DIR)
+
+debug: CFLAGS += -DDEBUG -g
+debug: BISONFLAGS += -Wcounterexamples
+debug: all
+
+sanitize: CFLAGS += -DDEBUG -g -fsanitize=address
+sanitize: all
+
+release: CFLAGS += -O2
+release: all
+
+clean:
+	-@rm -rvf $(BUILD)
+	-@rm -rvf {lexer.c,parser.c} {lexer.h,parser.h}

day_1/Makefile

@@ -1,54 +1,3 @@
-CC := clang
-YACC := bison
-LEX := flex
-CFLAGS := -std=c17 -Wpedantic -Wall -Wextra
-BUILD := ./build
-INCLUDE	:= -I./
-OBJ_DIR := $(BUILD)/objects
-APP_DIR := $(BUILD)/bin
 TARGET := day_1
 
-SRC := $(wildcard ./*.cpp) lexer.c parser.c
+include ../Makefile.common.mk
-
-OBJECTS	:= $(SRC:%.c=$(OBJ_DIR)/%.o)
-
-# targets
-all: build $(APP_DIR)/$(TARGET)
-
-run: all
-	$(APP_DIR)/$(TARGET)
-
-flex:
-	$(LEX) --outfile=lexer.c --header-file=lexer.h lexer.l
-
-bison:
-	$(YACC) --output=parser.c parser.y
-
-generate: flex bison
-
-$(OBJ_DIR)/%.o: %.c
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) -o $@ -c $<
-
-$(APP_DIR)/$(TARGET): flex bison $(OBJECTS)
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) $(LDFLAGS) -o $(APP_DIR)/$(TARGET) $(OBJECTS)
-
-.PHONY: all build clean debug release
-
-build:
-	@mkdir -p $(APP_DIR)
-	@mkdir -p $(OBJ_DIR)
-
-debug: CFLAGS += -DDEBUG -g
-debug: all
-
-sanitize: CFLAGS += -DDEBUG -g -fsanitize=address
-sanitize: all
-
-release: CFLAGS += -O2
-release: all
-
-clean:
-	-@rm -rvf $(BUILD)
-	-@rm -rvf {lexer.c,parser.c} {lexer.h,parser.h}

day_10/Makefile

@@ -0,0 +1,3 @@
+TARGET := day_10
+
+include ../Makefile.common.mk

day_10/input.txt

@@ -0,0 +1,141 @@
+addx 1
+noop
+addx 5
+addx -1
+addx 5
+addx 1
+noop
+noop
+addx 2
+addx 5
+addx 2
+addx 1
+noop
+addx -21
+addx 26
+addx -6
+addx 8
+noop
+noop
+addx 7
+noop
+noop
+noop
+addx -37
+addx 13
+addx -6
+addx -2
+addx 5
+addx 25
+addx 2
+addx -24
+addx 2
+addx 5
+addx 5
+noop
+noop
+addx -2
+addx 2
+addx 5
+addx 2
+addx 7
+addx -2
+noop
+addx -8
+addx 9
+addx -36
+noop
+noop
+addx 5
+addx 6
+noop
+addx 25
+addx -24
+addx 3
+addx -2
+noop
+addx 3
+addx 6
+noop
+addx 9
+addx -8
+addx 5
+addx 2
+addx -7
+noop
+addx 12
+addx -10
+addx 11
+addx -38
+addx 22
+addx -15
+addx -3
+noop
+addx 32
+addx -25
+addx -7
+addx 11
+addx 5
+addx 10
+addx -9
+addx 17
+addx -12
+addx 2
+noop
+addx 2
+addx -15
+addx 22
+noop
+noop
+noop
+addx -35
+addx 7
+addx 21
+addx -25
+noop
+addx 3
+addx 2
+noop
+addx 7
+noop
+addx 3
+noop
+addx 2
+addx 9
+addx -4
+addx -2
+addx 5
+addx 2
+addx -2
+noop
+addx 7
+addx 2
+addx -39
+addx 2
+noop
+addx 1
+noop
+addx 5
+addx 24
+addx -20
+addx 1
+addx 5
+noop
+noop
+addx 4
+noop
+addx 1
+noop
+addx 4
+addx 3
+noop
+addx 2
+noop
+noop
+addx 1
+addx 2
+noop
+addx 3
+noop
+noop
+

day_10/lexer.l

@@ -0,0 +1,51 @@
+%{
+#include <stdio.h>
+#include <stdlib.h>
+#include "parser.h"
+
+%}
+
+%option warn nodefault
+
+/* makes the scanner terminate after reaching <<EOF>> instead of assuming a new input was provided */
+%option noyywrap
+/* disable some unused functionality, add scanner tracking */
+%option nounput noinput batch debug
+
+/* gimme a reentrant parser (overkill but more pure) */
+%option reentrant
+
+%option bison-bridge
+
+
+NL                  [\n]
+SPACE               " "
+
+NOP                 "noop"
+ADD                 "addx"
+
+/*general definitions*/
+NUM                 [0-9\-]
+
+%%
+
+{NL}                { return NEWLINE; }
+{SPACE}             { /* return SPACE; */ }
+{NOP}               { return NOP; }
+{ADD}               { return ADDX; }
+
+{NUM}+              {
+                        int num = atoi(yytext);
+                        yylval->num = num;
+                        return NUM;
+                    }
+
+<<EOF>>             {
+                        return END_OF_FILE;
+                    }
+.                   {
+                        printf("[error] Encountered unexpected token %s\n", yytext);
+                        return 0;
+                    }
+
+%%

day_10/parser.y

@@ -0,0 +1,132 @@
+/* Require bison minimal version */
+%require "3.2"
+
+/* write out a header file containing the token defines */
+%header
+
+// Code for the header file generated by bison
+%code requires {
+    #include <stdbool.h>
+
+    typedef void* yyscan_t;
+
+    struct parser_state {
+        /// Program Counter
+        size_t cycle;
+
+        /// Contents of register X
+        long reg;
+
+        /// Task 1
+        long sum;
+        size_t next_target_cycle;
+    };
+}
+
+// Code for the c file
+%{
+    #include <stdio.h>
+    #include <stdlib.h>
+    #include "parser.h"
+    #include "lexer.h"
+
+    void yyerror(struct parser_state* state, yyscan_t scanner, const char* msg) {
+        (void)state;
+        (void)scanner;
+        fprintf(stderr, "\033[93mSyntax Error: %s\033[0m\n", msg);
+    }
+
+    void increment_cycle(struct parser_state *state) {
+        state->cycle++;
+
+        if (state->cycle == state->next_target_cycle) {
+            long tmp = state->cycle * state->reg;
+            printf("[info] Register contents at cycle %zu: %ld\n", state->cycle, state->reg);
+            state->sum += tmp;
+
+            if (state->next_target_cycle < 220) {
+                state->next_target_cycle += 40;
+            }
+        }
+    }
+%}
+
+// define a reentrant parser
+%define api.pure
+
+// enable parser tracing and detailed error messages (plus Lookahead Correction)
+%define parse.trace
+%define parse.error detailed
+%define parse.lac full
+
+%lex-param   { yyscan_t scanner }
+%parse-param { struct parser_state* state }
+%parse-param { yyscan_t scanner }
+
+%union {
+    int num;
+}
+
+%start input
+%token NEWLINE
+%token NOP ADDX
+%token <num> NUM
+%term END_OF_FILE
+
+%%
+
+input
+    : line input
+    | END_OF_FILE   { return 0; }
+    ;
+
+line
+    : instruction NEWLINE
+    | NEWLINE
+    ;
+
+instruction
+    : NOP       { increment_cycle(state); }
+    | ADDX NUM  {
+                    increment_cycle(state);
+                    increment_cycle(state);
+
+                    state->reg += $2;
+                }
+    ;
+
+
+%%
+
+
+int main(void) {
+    struct parser_state *state = calloc(1, sizeof(struct parser_state));
+    if (!state) {
+        fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+        return EXIT_FAILURE;
+    }
+
+    state->reg = 1;
+    state->next_target_cycle = 20;
+
+    yyscan_t scanner;
+    if (yylex_init(&scanner)) {
+        fprintf(stderr, "\033[91m[error] Could not initialize lexer\033[0m\n");
+        return EXIT_FAILURE;
+    }
+
+    if (yyparse(state, scanner)) {
+		// TODO: Error handling https://www.gnu.org/software/bison/manual/html_node/Parser-Function.html
+		// error during parse occured
+		return EXIT_FAILURE;
+	}
+
+    yylex_destroy(scanner);
+
+    // task 1
+    printf("Sum of signal strengths: %ld\n", state->sum);
+
+    free(state);
+
+    return 0;
+}

day_2-1/Makefile

@@ -1,54 +1,3 @@
-CC := clang
+TARGET := day_2_1
-YACC := bison
-LEX := flex
-CFLAGS := -std=c17 -Wpedantic -Wall -Wextra
-BUILD := ./build
-INCLUDE	:= -I./
-OBJ_DIR := $(BUILD)/objects
-APP_DIR := $(BUILD)/bin
-TARGET := day_2
 
-SRC := $(wildcard ./*.cpp) lexer.c parser.c
+include ../Makefile.common.mk
-
-OBJECTS	:= $(SRC:%.c=$(OBJ_DIR)/%.o)
-
-# targets
-all: build $(APP_DIR)/$(TARGET)
-
-run: all
-	$(APP_DIR)/$(TARGET)
-
-flex:
-	$(LEX) --outfile=lexer.c --header-file=lexer.h lexer.l
-
-bison:
-	$(YACC) --output=parser.c parser.y
-
-generate: flex bison
-
-$(OBJ_DIR)/%.o: %.c
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) -o $@ -c $<
-
-$(APP_DIR)/$(TARGET): flex bison $(OBJECTS)
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) $(LDFLAGS) -o $(APP_DIR)/$(TARGET) $(OBJECTS)
-
-.PHONY: all build clean debug release
-
-build:
-	@mkdir -p $(APP_DIR)
-	@mkdir -p $(OBJ_DIR)
-
-debug: CFLAGS += -DDEBUG -g
-debug: all
-
-sanitize: CFLAGS += -DDEBUG -g -fsanitize=address
-sanitize: all
-
-release: CFLAGS += -O2
-release: all
-
-clean:
-	-@rm -rvf $(BUILD)
-	-@rm -rvf {lexer.c,parser.c} {lexer.h,parser.h}

day_2-2/Makefile

@@ -1,54 +1,3 @@
-CC := clang
+TARGET := day_2_2
-YACC := bison
-LEX := flex
-CFLAGS := -std=c17 -Wpedantic -Wall -Wextra
-BUILD := ./build
-INCLUDE	:= -I./
-OBJ_DIR := $(BUILD)/objects
-APP_DIR := $(BUILD)/bin
-TARGET := day_2
 
-SRC := $(wildcard ./*.cpp) lexer.c parser.c
+include ../Makefile.common.mk
-
-OBJECTS	:= $(SRC:%.c=$(OBJ_DIR)/%.o)
-
-# targets
-all: build $(APP_DIR)/$(TARGET)
-
-run: all
-	$(APP_DIR)/$(TARGET)
-
-flex:
-	$(LEX) --outfile=lexer.c --header-file=lexer.h lexer.l
-
-bison:
-	$(YACC) --output=parser.c parser.y
-
-generate: flex bison
-
-$(OBJ_DIR)/%.o: %.c
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) -o $@ -c $<
-
-$(APP_DIR)/$(TARGET): flex bison $(OBJECTS)
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) $(LDFLAGS) -o $(APP_DIR)/$(TARGET) $(OBJECTS)
-
-.PHONY: all build clean debug release
-
-build:
-	@mkdir -p $(APP_DIR)
-	@mkdir -p $(OBJ_DIR)
-
-debug: CFLAGS += -DDEBUG -g
-debug: all
-
-sanitize: CFLAGS += -DDEBUG -g -fsanitize=address
-sanitize: all
-
-release: CFLAGS += -O2
-release: all
-
-clean:
-	-@rm -rvf $(BUILD)
-	-@rm -rvf {lexer.c,parser.c} {lexer.h,parser.h}

day_4/Makefile

@@ -1,54 +1,3 @@
-CC := clang
-YACC := bison
-LEX := flex
-CFLAGS := -std=c17 -Wpedantic -Wall -Wextra
-BUILD := ./build
-INCLUDE	:= -I./
-OBJ_DIR := $(BUILD)/objects
-APP_DIR := $(BUILD)/bin
 TARGET := day_4
 
-SRC := $(wildcard ./*.cpp) lexer.c parser.c
+include ../Makefile.common.mk
-
-OBJECTS	:= $(SRC:%.c=$(OBJ_DIR)/%.o)
-
-# targets
-all: build $(APP_DIR)/$(TARGET)
-
-run: all
-	$(APP_DIR)/$(TARGET)
-
-flex:
-	$(LEX) --outfile=lexer.c --header-file=lexer.h lexer.l
-
-bison:
-	$(YACC) --output=parser.c parser.y
-
-generate: flex bison
-
-$(OBJ_DIR)/%.o: %.c
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) -o $@ -c $<
-
-$(APP_DIR)/$(TARGET): flex bison $(OBJECTS)
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) $(LDFLAGS) -o $(APP_DIR)/$(TARGET) $(OBJECTS)
-
-.PHONY: all build clean debug release
-
-build:
-	@mkdir -p $(APP_DIR)
-	@mkdir -p $(OBJ_DIR)
-
-debug: CFLAGS += -DDEBUG -g
-debug: all
-
-sanitize: CFLAGS += -DDEBUG -g -fsanitize=address
-sanitize: all
-
-release: CFLAGS += -O2
-release: all
-
-clean:
-	-@rm -rvf $(BUILD)
-	-@rm -rvf {lexer.c,parser.c} {lexer.h,parser.h}

day_5/Makefile

@@ -1,56 +1,3 @@
-CC := clang
-YACC := bison
-LEX := flex
-CFLAGS := -std=c17 -Wpedantic -Wall -Wextra
-BISONFLAGS := 
-BUILD := ./build
-INCLUDE	:= -I./
-OBJ_DIR := $(BUILD)/objects
-APP_DIR := $(BUILD)/bin
 TARGET := day_5
 
-SRC := $(wildcard ./*.cpp) lexer.c parser.c
+include ../Makefile.common.mk
-
-OBJECTS	:= $(SRC:%.c=$(OBJ_DIR)/%.o)
-
-# targets
-all: build $(APP_DIR)/$(TARGET)
-
-run: all
-	$(APP_DIR)/$(TARGET)
-
-flex:
-	$(LEX) --outfile=lexer.c --header-file=lexer.h lexer.l
-
-bison:
-	$(YACC) $(BISONFLAGS) --output=parser.c parser.y
-
-generate: flex bison
-
-$(OBJ_DIR)/%.o: %.c
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) -o $@ -c $<
-
-$(APP_DIR)/$(TARGET): flex bison $(OBJECTS)
-	@mkdir -p $(@D)
-	$(CC) $(CFLAGS) $(INCLUDE) $(LDFLAGS) -o $(APP_DIR)/$(TARGET) $(OBJECTS)
-
-.PHONY: all build clean debug release
-
-build:
-	@mkdir -p $(APP_DIR)
-	@mkdir -p $(OBJ_DIR)
-
-debug: CFLAGS += -DDEBUG -g
-debug: BISONFLAGS += -Wcounterexamples
-debug: all
-
-sanitize: CFLAGS += -DDEBUG -g -fsanitize=address
-sanitize: all
-
-release: CFLAGS += -O2
-release: all
-
-clean:
-	-@rm -rvf $(BUILD)
-	-@rm -rvf {lexer.c,parser.c} {lexer.h,parser.h}

day_5/parser.y

@@ -6,6 +6,8 @@
 
 // Code for the header file generated by bison
 %code requires {
+    #include <stdbool.h>
+
     typedef void* yyscan_t;
 
     #define NUM_PILES 9
@@ -20,6 +22,8 @@
         // points to the topmost item in the stack
         struct stack_item** stacks;
         unsigned stack_idx;
+        // whether the crane is generation two (task 2)
+        bool is_gen_two;
     };
 }
 
@@ -27,6 +31,7 @@
 %{
     #include <stdio.h>
     #include <stdlib.h>
+    #include <stdbool.h>
     #include "parser.h"
     #include "lexer.h"
 
@@ -115,32 +120,58 @@ expr
     : MOVE_OP NUMBER ORIGIN NUMBER DEST NUMBER {
         // Source: $4, Dst: $6, repeat $2 times
         // printf("move %lu from %lu to %lu", $2, $4, $6);
-        for (unsigned long i = 0; i < $2; i++) {
-            // get the current element
-            struct stack_item* it = state->stacks[$4 -1];
 
-            if (!it) {
+        if (state->is_gen_two) {
-                // TODO(feliix42): use yyerror?
+            struct stack_item* it = state->stacks[$4 - 1];
-                fprintf(stderr, "\033[91m[parser error] tried to pop from empty stack\n\033[0m");
+            for (unsigned long i = 1; i < $2; i++) {
-                break;
+                if (!it) {
+                    // TODO(feliix42): use yyerror?
+                    fprintf(stderr, "\033[91m[parser error] tried to pop from empty stack\n\033[0m");
+                    break;
+                }
+
+                it = it->next;
             }
 
-            // delete old references
+            struct stack_item* tmp = state->stacks[$4 - 1];
-            state->stacks[$4 -1] = it->next;
+            state->stacks[$4 - 1] = it->next;
 
-            // insert on new stack
+            it->next = state->stacks[$6 - 1];
-            it->next = state->stacks[$6 -1];
+            state->stacks[$6 - 1] = tmp;
-            state->stacks[$6 -1] = it;
+        } else {
+            for (unsigned long i = 0; i < $2; i++) {
+                // get the current element
+                struct stack_item* it = state->stacks[$4 -1];
+
+                if (!it) {
+                    // TODO(feliix42): use yyerror?
+                    fprintf(stderr, "\033[91m[parser error] tried to pop from empty stack\n\033[0m");
+                    break;
+                }
+
+                // delete old references
+                state->stacks[$4 -1] = it->next;
+
+                // insert on new stack
+                it->next = state->stacks[$6 -1];
+                state->stacks[$6 -1] = it;
+            }
         }
     }
     ;
 
 %%
 
-int main(void) {
+int main(int argc, char** argv) {
     struct parser_state parser_state;
     parser_state.stack_idx = 0;
 
+    if (argc > 1 && argv[1][0] == '2') {
+        parser_state.is_gen_two = true;
+    } else {
+        parser_state.is_gen_two = false;
+    }
+
     parser_state.stacks = calloc(NUM_PILES, sizeof(struct stack_item*));
     if (!parser_state.stacks) {
         fprintf(stderr, "\033[91m[error] Could not initialize parser state\033[0m\n");

day_6/Makefile

@@ -0,0 +1,3 @@
+TARGET := day_6
+
+include ../Makefile.common.mk

day_6/input.txt

@@ -0,0 +1,2 @@
+hrbbjllllspssblslvvrdrbbpbbmcccfppvbbwvbbmrmjrjrfrgfgbffgfqfqlltlwttscsncscchssrppffvwwvvpnnwwwpvwvhhnvhhbttvzzdlzdlzzwmmjhhznnjdnnnqddbtdbdbsdsmdsdrrdpdwpdppgcgqgcctftsfszslljbljbjwbwbnwnqqrnnztntmtrmmzwzdwzwgwwwjhjsjgjtjjhpjhhppqzqdqffrvrtvvsmmgwmgwgbbclltctptzpzhpzptzppcfpcfftflfzftztddzgzmmfsmsrmmsstttvbvmbvvsmsqmqlldjdtthwtwbwggrzzjrzrcctffsshqshhpthhlnhlhqhdqqrwrmmcttpfttzfzgzdgdzzwrrtsrrsnrnccrbbsssbpbjjvzzwlwtwjwsjwjggzqgzzrsszzjnzjzwjzzcrzczncnqqztzfzhfhvvtjvjdvjjmrjrppvzppczpczcggshghvhnhhsrsnsdszzdpzpzlpzzhwwmnwmwmcwwfnwfwjjcbcncllcsllqdqzzhqhmqmbbjvjjwwcjjpnpllzfzddtmtccqrcrtrwrpphpmpplslmltthnnvhhvrvbblhhrrdqqmbqqgtqggdgcdcvvsbsswvvpggbbtftlflglzlmlbbfhhrshswhshffhhdnnrfrvrmrnrprrmfmpmnpnfnggvvcncdcrczrzccpmmssrbbdjdtdrdwrrwhrrvrtvvszvvwvzzmhhjhhwlhlqlvlttzftztdtstftrfrdddmtmzzsqzqvvpdpdcpcncnrrtntznzrzgznztnznhhsqqnrqrhhlzhzthhfddrzdrrqmqggcmmllnjjvwwjccfjfqfcfzccwvcwvcvjcjtjtnnqsqmqrmrzrszrszzfwfggnmmcdmdjmmhwwgfwfnwnlwwcffsrffvnvbvnvwnwgnwnmmbzbmbpplmplpspzpmzpzdzgzrzrtrjrbbppwvwgwmggqwgghqqshhcwcqwcqcfcbbnsnrrtztzrtrvtvhthzhmmrqqrwqqsjqjcctgtwthhqmmnffmgmdgdlgljjhwjwggrqqfrqqjvqvhqqgsqsgsttmrrbprbppmjppslpsllvlfvlvrvhvtqmrjcdzwsbzfmgmwmwqwhztqrsdzhqjqvbjbntnbndflthljcczdmmhszfgsplrtlqnfzbrlqngwdqtfwcmrdjrsmdpmjmqwrbwfjzwnvqhfmlqtvvnlfzbfccwslqpbzzjccbvrzhghqwtvqgwrmsfzqnmnqqjsjtpcmngpqgllfsnpqtjjbqcdppnsmtwrslnrbqtwvnbctzvwfmgctscmzjbqqgqdwbpzmrdwgfcjzftzgmfcjhchbnmnqnrgtqngwrmncjvptqqdtjtgtpzzdrfsdgmwlwrjnqldbwrqjrhwcczlzvlhpgrnwzhbwjnpthggczfgtrjnzvnlfdfbwcnzfbwlwlmgnnjnpvhbhqgnzhqsnmvbcftsmrcgpvnnnmgnrvpbzlpwnbwpzmwpgqvbfgjwfrjqnvvgmqwwcfddqmdznmfhpjcfgptqdqwmplrglbwlmsqzjshrlhflcjvptgrcfhjfgqmlfzrtphpbvcqzwpcnwljjdlmqzhcctqshdngrgtlfsrfccdtlvmqcdgnpcvphdsrpzfzwclvsqcpzqlfvvqzggdhpfzdvhshglvfzfmcllrdfjfsjtngjgddcpqnlmrnplwtlvwdvzftltnsnspcdztgqhlhvvbnwvnmhscfnqbngpvprzfrjcmfpfzfftrlnwgllhnjndpjdrwcgqpcgcqngnbfzlvzvhnqdjthflmwvppmbdssddmgsbgrqnpjzrjpzdddqgsdlmwnhhpjbthclvqhgrsnrbqgtnsjhncnzbhrdgftvbptrqssvsqfpqnddhmgwcrfqndqjsqgffmhdvqhjrdlmrlcqctqccprwlbqgqrwmtfhwmfjfqzdqbsdsjbtsvfvgbsrvqwnqqqqthpsqgcfslsqtnjwtsrcdcctggdghrjwpbfccrtwgszwbrsjswmjmjbcqrsgbcfsdjzsbjnnssnddnnvwgftlrqvphnqcgjszscrlhhjnljlqcjqtqfwbmdmrgdlcqqwmbsmsdhpplvlfglqwspbfptlbzqjwhqmfvzvsvpjclcdzsbvntmhdqdvhghcmmflpjbglsghbswdshtsbdrgpsrsclrmfwwqbrgdjsqztgttqpwhnfhszlgbfpzhczsnwqflmshlgbrpmdzgpqwtsbssgfjbtrwbmztlwwfmsdgpgfgdjfdccwlfgztbcbqjvjtvslmddjplrswwcszspgplsrhrnwnmrrfbcgdmntcrlvnfqtwwcczsglrhtrfqnmhvgzjpmlplqvqhmnfgvzqcmzhqszgslvndqtqhvrbvbmclbcbjdswvcjrzgfdmdwnnlzlzqcffsrqdfmmpzfnmdsnqlpcrhzsdnsflblcjsfsgcnsspftjrlmdjsmfpqtmlgfvnlfnjscsgwzwvpjrvvclhsbqldlnmtglhbjfwlzmvrbvgtprfjbjhhnlqnbrswwlqtcgrjrltdrnfrjhrntllptlsbhqrwvdsfrlghtfcndznzjwcgmtdvffltgrdmljlqhdtmdvnfsfsrvdpmhlrrsttvqlwfptddwbpfrbclwwzmfpttmrmmqzjnbbnnfvzwmmcfshvrlbdbjzprftbqvdsghnnzwbjccpthdsvsdlgvphsgjdqjwsgmzqnqpqvgqjvwgjtzpmqqwnlwrwhqqjjclcbhjgpwhqdclwmqfmwbwmwwvcbhfznfhcfbprfcdqlbcttnvgnjwswcmpbrghtzgdbppbprffzjgvddzpwmdctrhnrfzdfhtmnfrsfdqvzcnrtncflhvldcndwqtvbggmwlzhchlcwtcbqcvlfhdwljgddwpvcfczvfqmphgtdsnsqwdpvvmwnwqjbrjwbdhhgtffphsdrvspsbgmfrmwmhnrgqdfppzgfpgmqjcsnglczgwhjthfhztzrlpgzjhcfrjpjvtjptptbvflftjtcfhmbwlhlbhvnjnbfmwjrgbvvhmdlncdgncgfjcnnpdljfcjsmsfscqpwsgcmlhhqmldsnjfrrqpghwncmgwgnjsdtvbhrbbnmpqjrrctqqnqzztmbqmdsgdvmmlwmbvprllzgntnmttrlzrttmjjlrwpwmtfznmwnsjmjhjdnsppfhcrjpzhjqzdtdbsjshfzzvrwvjbjbgtsfpgggbdztczwlhpmthfjdgsbrvlwmlrvgdrpjzccwmgpcnqqzmqdjqmwsrzwsmtmdjdhmjrwfwnzlmfnqtcgtslwtlnwhvmqntmglhntnsjlnmzfvfdztcfwmpchsrsdmqvqcwljzrmmssjvbmvvnmqlbsdwnrbmqctdtmfzlgfzpmjcnftgftvjpfbwwmzfdrrwjwcfwfcfmzbbnppgjrmbcvmvnjpdrzmvndvddtvshlnjjwgtsvnwtwnhcbfpnthpjlrhgrqccdgppjvdqjwqrfrrgnvhfwvjhnwhntnpmghphrtgqhwtbrqhqljfdjbgnlgmqqgfcqpqfhcpgspdbvlbfjvlrgmtjztwdzlrhqwwtcpdvsqgssjbjjgqlwbcctzzqvvmdzpfrmspmqhtzwgcfsslpnhpjfwqrrfbwbndrvhnnsjnlvlvqdsgwzjsrprhgtvsfbhbcpljdczbtdwzcnhzntrwcrjctmhtjfdlthznzmqblppzcqgpjhlzjrmcvpptfjjzltdhmvwphwlccscwrwfcqpqwwrzcmnltzdcfvtjrcvsqwtchrmdfzjmzjfhppjzbhglwqggzqqnspfmzrfwrqdqdrsdbsdhcgdqrrnjlwrqhfhpzjhrvjndqphndnnnbwhrjvqrrbvlhhbljjcwmfpvnhcszfshlsnczgtcfhjslbhzczdqdmdnvqdzhbmbpcnbntwgllfscrcwhfrgtfvftmwhbgfhjzjrbvvwc
+

day_6/lexer.l

@@ -0,0 +1,41 @@
+%{
+#include <stdio.h>
+#include <stdlib.h>
+#include "parser.h"
+%}
+
+%option warn nodefault
+
+/* makes the scanner terminate after reaching <<EOF>> instead of assuming a new input was provided */
+%option noyywrap
+/* disable some unused functionality, add scanner tracking */
+%option nounput noinput batch debug
+
+/* gimme a reentrant parser (overkill but more pure) */
+%option reentrant
+
+%option bison-bridge
+
+
+NL                  [\n]
+CHAR                [a-z]
+
+
+%%
+
+{NL}                {
+                        return NEWLINE;
+                    }
+{CHAR}              {
+                        yylval->cval = yytext[0];
+                        return CHAR;
+                    }
+<<EOF>>             {
+                        return END_OF_FILE;
+                    }
+.                   {
+                        printf("[error] Encountered unexpected token %s\n", yytext);
+                        return 0;
+                    }
+
+%%

day_6/parser.y

@@ -0,0 +1,187 @@
+/* Require bison minimal version */
+%require "3.2"
+
+/* write out a header file containing the token defines */
+%header
+
+// Code for the header file generated by bison
+%code requires {
+    #include <stdbool.h>
+
+    #define BUFSIZE 14
+
+    typedef void* yyscan_t;
+
+    struct parser_state {
+        // for storing the most recently read 14 chars
+        char buffer[BUFSIZE];
+        // location tracker
+        unsigned long loc;
+
+        bool found_start_of_packet;
+        unsigned long packet_start;
+
+        bool found_start_of_msg;
+        unsigned long msg_start;
+
+        bool check_matrix[26];
+    };
+}
+
+// Code for the c file
+%{
+    #include <stdio.h>
+    #include <stdlib.h>
+    #include <stdbool.h>
+    #include "parser.h"
+    #include "lexer.h"
+
+    void yyerror(struct parser_state* state, yyscan_t scanner, const char* msg) {
+        (void)state;
+        (void)scanner;
+        fprintf(stderr, "\033[93mSyntax Error: %s\033[0m\n", msg);
+    }
+%}
+
+// define a reentrant parser
+%define api.pure
+
+// enable parser tracing and detailed error messages (plus Lookahead Correction)
+%define parse.trace
+%define parse.error detailed
+%define parse.lac full
+
+%lex-param   { yyscan_t scanner }
+%parse-param { struct parser_state* state }
+%parse-param { yyscan_t scanner }
+
+%union {
+    char cval;
+}
+
+
+%start input
+%token NEWLINE
+%token <cval> CHAR
+%term END_OF_FILE
+
+%%
+
+input
+    : msg blanks END_OF_FILE   { return 0; }
+    ;
+
+blanks
+    : NEWLINE blanks
+    | NEWLINE
+    ;
+
+msg
+    : bit msg
+    | bit
+    ;
+
+bit
+    : CHAR              {
+                            if (!state->found_start_of_packet || !state->found_start_of_msg) {
+                                state->loc++;
+
+                                // left shift existing data
+                                for (int i = 0; i < (BUFSIZE-1); i++) {
+                                    state->buffer[i] = state->buffer[i+1];
+                                }
+
+                                state->buffer[BUFSIZE-1] = $1;
+
+                                // check whether condition is met
+                                // offset array indices by the base -- 'a'
+                                char offset = 'a';
+
+                                // Search for start of packet
+                                bool search_sop = !state->found_start_of_packet; // sop - start of packet
+                                bool search_som = !state->found_start_of_msg; // som - start of message
+
+                                if (search_sop) {
+                                    state->found_start_of_packet = true;
+                                }
+                                if (search_som) {
+                                    state->found_start_of_msg = true;
+                                }
+
+                                // the start of packet only concerns itself with the last 4 characters read; the start of message with the last 14
+                                // hence, we check the last 4 first, then the rest
+                                for (int i = BUFSIZE - 4; i < BUFSIZE; i++) {
+                                    if (!state->check_matrix[state->buffer[i] - offset]) {
+                                        state->check_matrix[state->buffer[i] - offset] = true;
+                                    } else {
+                                        if (search_sop) {
+                                            state->found_start_of_packet = false;
+                                        }
+                                        if (search_som) {
+                                            state->found_start_of_msg = false;
+                                        }
+                                        break;
+                                    }
+                                }
+
+                                // now check the remaining elements
+                                for (int i = 0; i < BUFSIZE - 4; i++) {
+                                    if (!state->check_matrix[state->buffer[i] - offset]) {
+                                        state->check_matrix[state->buffer[i] - offset] = true;
+                                    } else {
+                                        if (search_som) {
+                                            state->found_start_of_msg = false;
+                                        }
+                                        break;
+                                    }
+                                }
+                                
+
+                                if (search_sop && state->found_start_of_packet) {
+                                    state->packet_start = state->loc;
+                                }
+                                if (search_som && state->found_start_of_msg) {
+                                    state->msg_start = state->loc;
+                                }
+
+                                // housekeeping; reset the fields to false
+                                for (int i = 0; i < BUFSIZE; i++) {
+                                    state->check_matrix[state->buffer[i] - offset] = false;
+                                }
+                            }
+                        }
+    ;
+
+
+%%
+
+int main(void) {
+    struct parser_state parser_state;
+    for (int i = 0; i < BUFSIZE; i++) {
+        parser_state.buffer[i] = 'a';
+    }
+    parser_state.loc = 0;
+    parser_state.packet_start = 0;
+    parser_state.msg_start = 0;
+    parser_state.found_start_of_packet = false;
+    parser_state.found_start_of_msg = false;
+
+    yyscan_t scanner;
+    if (yylex_init(&scanner)) {
+        fprintf(stderr, "\033[91m[error] Could not initialize lexer\033[0m\n");
+        return EXIT_FAILURE;
+    }
+
+    if (yyparse(&parser_state, scanner)) {
+		// TODO: Error handling https://www.gnu.org/software/bison/manual/html_node/Parser-Function.html
+		// error during parse occured
+		return EXIT_FAILURE;
+	}
+
+    yylex_destroy(scanner);
+
+    printf("First start-of-packet marker detected at: %lu\n", parser_state.packet_start);
+    printf("First start-of-message marker detected at: %lu\n", parser_state.msg_start);
+
+    return 0;
+}

day_7/Makefile

@@ -0,0 +1,3 @@
+TARGET := day_7
+
+include ../Makefile.common.mk

day_7/filetree.c

@@ -0,0 +1,30 @@
+#include "filetree.h"
+#include <stdlib.h>
+
+void add_directory(struct dirnode *cur, struct dirnode *item) {
+    // NOTE(feliix42): I'm aware that this is super inefficient, but who cares
+    struct dirnode **items = realloc(cur->directories, (cur->num_dirs + 1) * sizeof(struct dirnode *));
+
+    if (!items) {
+        fprintf(stderr, "\033[93m[error] Failed to allocate memory\033[0m\n");
+        return;
+    }
+
+    cur->directories = items;
+    cur->directories[cur->num_dirs] = item;
+    cur->num_dirs++;
+}
+
+void add_file(struct dirnode *cur, struct filenode *item) {
+    // NOTE(feliix42): I'm aware that this is super inefficient, but who cares
+    struct filenode **items = realloc(cur->files, (cur->num_files + 1) * sizeof(struct filenode *));
+
+    if (!items) {
+        fprintf(stderr, "\033[93m[error] Failed to allocate memory\033[0m\n");
+        return;
+    }
+
+    cur->files = items;
+    cur->files[cur->num_files] = item;
+    cur->num_files++;
+}

day_7/filetree.h

@@ -0,0 +1,30 @@
+#ifndef FILETREE_H
+#define FILETREE_H
+
+#include <stdlib.h>
+#include <stdio.h>
+
+struct filenode {
+    char *name;
+
+    unsigned long size;
+};
+
+struct dirnode {
+    char *name;
+
+    struct filenode **files;
+    size_t num_files;
+
+    struct dirnode **directories;
+    size_t num_dirs;
+
+    unsigned long size;
+};
+
+void add_directory(struct dirnode *cur, struct dirnode *item);
+void add_file(struct dirnode *cur, struct filenode *item);
+
+
+
+#endif // FILETREE_H

day_7/input.txt

@@ -0,0 +1,984 @@
+$ cd /
+$ ls
+dir gqcclj
+dir lmtpm
+dir nhqwt
+dir qcq
+dir vwqwlqrt
+$ cd gqcclj
+$ ls
+62425 dqp.gjm
+174181 hrtw.qsd
+273712 pflp.mdw
+169404 zlthnlhf.mtn
+180878 zprprf
+$ cd ..
+$ cd lmtpm
+$ ls
+dir clffsvcw
+163587 cvcl.jqh
+dir dcqnblb
+dir dtpwln
+dir fvt
+dir hrcrw
+dir jdqzmqn
+236754 nrdmlj
+205959 pflp.mdw
+dir qcq
+dir rsn
+129926 vdgcqdn.sqd
+dir zprprf
+$ cd clffsvcw
+$ ls
+6997 dcqnblb.wbh
+145711 dqp
+159225 pflp.mdw
+$ cd ..
+$ cd dcqnblb
+$ ls
+dir dcqnblb
+dir gfn
+dir lpswsp
+dir lvt
+dir zprprf
+$ cd dcqnblb
+$ ls
+2020 grpdmd.ggz
+dir zpswzfvg
+$ cd zpswzfvg
+$ ls
+206998 zprprf.gnw
+$ cd ..
+$ cd ..
+$ cd gfn
+$ ls
+277530 rhbvtblc.mvw
+$ cd ..
+$ cd lpswsp
+$ ls
+173180 dcqnblb
+$ cd ..
+$ cd lvt
+$ ls
+dir hjllwsvl
+dir ptbt
+$ cd hjllwsvl
+$ ls
+dir wqnc
+$ cd wqnc
+$ ls
+64695 grpdmd.ggz
+$ cd ..
+$ cd ..
+$ cd ptbt
+$ ls
+150880 vvbt.gtp
+$ cd ..
+$ cd ..
+$ cd zprprf
+$ ls
+dir ldzslndn
+dir qftt
+$ cd ldzslndn
+$ ls
+dir bwqqsbhg
+129454 vbn
+$ cd bwqqsbhg
+$ ls
+108701 zprprf.gss
+$ cd ..
+$ cd ..
+$ cd qftt
+$ ls
+64268 cvcl.jqh
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd dtpwln
+$ ls
+196215 cvcl.jqh
+dir dpwg
+dir ldzslndn
+dir znnsqqh
+$ cd dpwg
+$ ls
+192388 gmh
+47754 grgzh.qdl
+99449 hqsh
+dir pbmf
+50061 pflp.mdw
+192902 qcq.pgg
+dir rmpvj
+dir scgc
+$ cd pbmf
+$ ls
+210083 wpfnwbl.mgf
+$ cd ..
+$ cd rmpvj
+$ ls
+125738 nmlnbvrd
+226214 zprprf.jnp
+114257 zprprf.srs
+$ cd ..
+$ cd scgc
+$ ls
+182115 rrc.rcc
+$ cd ..
+$ cd ..
+$ cd ldzslndn
+$ ls
+201992 qcrm.cpd
+$ cd ..
+$ cd znnsqqh
+$ ls
+85635 cvcl.jqh
+$ cd ..
+$ cd ..
+$ cd fvt
+$ ls
+dir dcqnblb
+dir gnc
+75864 vfn
+$ cd dcqnblb
+$ ls
+dir dcqnblb
+dir lbnflwsh
+$ cd dcqnblb
+$ ls
+269901 cvcl.jqh
+$ cd ..
+$ cd lbnflwsh
+$ ls
+33336 grpdmd.ggz
+42861 phg.wmc
+$ cd ..
+$ cd ..
+$ cd gnc
+$ ls
+dir jhjbjsp
+dir jjppr
+$ cd jhjbjsp
+$ ls
+96177 ldzslndn
+$ cd ..
+$ cd jjppr
+$ ls
+181016 dqp
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd hrcrw
+$ ls
+261376 dtjfpppr.dww
+54658 vsrgvw.pfn
+$ cd ..
+$ cd jdqzmqn
+$ ls
+52342 dcpndc.vlg
+171946 gggpchh.tbb
+dir ldzslndn
+11156 nbfrfvv.gzw
+$ cd ldzslndn
+$ ls
+107873 cvcl.jqh
+216034 gfdjrbz
+68844 pqllfrrh.jcf
+$ cd ..
+$ cd ..
+$ cd qcq
+$ ls
+152886 ldzslndn.ltn
+105125 vwplh.vbf
+$ cd ..
+$ cd rsn
+$ ls
+15385 hqcmjdgv.jjv
+105735 qcq.bzg
+58805 snczcsp
+26668 vbn
+$ cd ..
+$ cd zprprf
+$ ls
+dir chbmq
+dir dcqnblb
+dir dqp
+dir nfspb
+89506 zprprf.hnt
+$ cd chbmq
+$ ls
+dir cnjvw
+dir dqp
+151434 frsvrdnt
+dir msztjvcb
+240689 qcq.jlh
+dir sjzrcg
+97312 vnr.zfr
+dir zprprf
+$ cd cnjvw
+$ ls
+dir bpbs
+252403 cqhtshc
+dir djmjhn
+10935 fhqmswr
+6582 pdwml.ldd
+dir qcq
+219282 rfmd
+$ cd bpbs
+$ ls
+147582 bnhwsnsj.gdm
+61362 cvcl.jqh
+152857 vdgcqdn.sqd
+$ cd ..
+$ cd djmjhn
+$ ls
+dir bjdbcjbb
+dir dcqnblb
+dir dqp
+dir lgdwtt
+$ cd bjdbcjbb
+$ ls
+110710 cvcl.jqh
+252792 hmshctr.lgz
+dir mjhtmbj
+189745 shsswcgr
+dir tfnhp
+194940 vbn
+dir zprprf
+$ cd mjhtmbj
+$ ls
+dir dqp
+dir hbthpcmb
+$ cd dqp
+$ ls
+200832 sbcrz.qgw
+$ cd ..
+$ cd hbthpcmb
+$ ls
+55191 ffcntg
+$ cd ..
+$ cd ..
+$ cd tfnhp
+$ ls
+276825 dqp
+161538 gqmr.wgb
+$ cd ..
+$ cd zprprf
+$ ls
+287638 dcqnblb.ssp
+41274 hgmrvj.mwf
+249118 sbb.gsf
+105141 wwrg.gqz
+$ cd ..
+$ cd ..
+$ cd dcqnblb
+$ ls
+1957 btmmc
+32386 dtzbzg.dhm
+dir mmrbj
+98283 ntmhfgtl.pmf
+dir zprprf
+$ cd mmrbj
+$ ls
+273194 wnsq
+251527 zprprf
+$ cd ..
+$ cd zprprf
+$ ls
+27678 ldzslndn.rrl
+62866 ljf.fdj
+148502 qcq.dlg
+dir rvgqvm
+179231 tllnmhn.pjp
+64033 vbn
+dir zcdrj
+$ cd rvgqvm
+$ ls
+dir ntbv
+262324 prhgj.szz
+dir qbvdh
+$ cd ntbv
+$ ls
+116608 cgv.fvj
+175200 swpswq.twt
+$ cd ..
+$ cd qbvdh
+$ ls
+160353 sdhfrb.wjn
+$ cd ..
+$ cd ..
+$ cd zcdrj
+$ ls
+283262 ctl
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd dqp
+$ ls
+dir jfzm
+111438 rdrgb.mjf
+64194 wgtmqrq
+dir zprprf
+$ cd jfzm
+$ ls
+158774 pflp.mdw
+$ cd ..
+$ cd zprprf
+$ ls
+215264 sgsstcp
+$ cd ..
+$ cd ..
+$ cd lgdwtt
+$ ls
+dir qcq
+$ cd qcq
+$ ls
+165461 ldzslndn.vvb
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd qcq
+$ ls
+dir dpd
+165044 grpdmd.ggz
+82343 ldzslndn
+dir mwg
+176689 psjcwp.wct
+44404 qcq.zwd
+$ cd dpd
+$ ls
+84087 dqp
+227386 zprprf.gfs
+$ cd ..
+$ cd mwg
+$ ls
+214086 pflp.mdw
+dir sjjsdn
+225859 wcdt
+158892 zprprf.frs
+$ cd sjjsdn
+$ ls
+260121 gplgp.dfn
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd dqp
+$ ls
+dir hcrwclpg
+dir zphd
+$ cd hcrwclpg
+$ ls
+dir cmqntjj
+16393 ldzslndn.qbm
+91152 qqdtc.zdq
+$ cd cmqntjj
+$ ls
+272266 ldzslndn.pll
+$ cd ..
+$ cd ..
+$ cd zphd
+$ ls
+165711 chftwcsw.fqw
+256871 cvcl.jqh
+251168 zprprf.gfv
+$ cd ..
+$ cd ..
+$ cd msztjvcb
+$ ls
+206231 brzn.lmn
+dir dcqnblb
+21571 dqp
+dir fmn
+45779 mlfctz.cjr
+288827 pflp.mdw
+220578 qcq.fqf
+$ cd dcqnblb
+$ ls
+198121 ghbwgs
+93681 nmqhl.vpq
+$ cd ..
+$ cd fmn
+$ ls
+29407 mdfws.qvs
+$ cd ..
+$ cd ..
+$ cd sjzrcg
+$ ls
+155120 ddclvsjr.rpq
+136029 ldzslndn.dcm
+dir vhzh
+$ cd vhzh
+$ ls
+212446 vbn
+$ cd ..
+$ cd ..
+$ cd zprprf
+$ ls
+240335 crt.gqh
+185363 gnmm.qgh
+dir ldzslndn
+dir nwl
+dir qll
+277043 vbn
+217796 vtvgpdl.vtm
+$ cd ldzslndn
+$ ls
+273570 cvcl.jqh
+68510 fgdmz.hrc
+dir npq
+dir swjrzzrm
+$ cd npq
+$ ls
+97923 dzcjsqwt
+$ cd ..
+$ cd swjrzzrm
+$ ls
+180599 tmpgn.bjf
+$ cd ..
+$ cd ..
+$ cd nwl
+$ ls
+171833 dlwrfhh.qgn
+$ cd ..
+$ cd qll
+$ ls
+219926 dcqnblb.bvn
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd dcqnblb
+$ ls
+dir lvpb
+276198 tbgcm.qct
+$ cd lvpb
+$ ls
+142590 bvhjlld
+268259 gnjfg.sgb
+dir qcq
+206220 qcq.zsg
+258137 rrsw.dnb
+dir tmr
+215549 vbn
+$ cd qcq
+$ ls
+dir mmpgd
+dir tdsz
+dir tmfvsjwc
+$ cd mmpgd
+$ ls
+70793 jwbnpwnn
+$ cd ..
+$ cd tdsz
+$ ls
+246310 tdvrhhg.bzq
+$ cd ..
+$ cd tmfvsjwc
+$ ls
+103899 grpdmd.ggz
+287850 ldzslndn
+125930 llhr
+$ cd ..
+$ cd ..
+$ cd tmr
+$ ls
+83344 fbtfcg.hqp
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd dqp
+$ ls
+dir lbgmcbv
+dir nbg
+$ cd lbgmcbv
+$ ls
+81776 wzdzzdp
+$ cd ..
+$ cd nbg
+$ ls
+dir mfsgjp
+155574 pflp.mdw
+$ cd mfsgjp
+$ ls
+199400 vdgcqdn.sqd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd nfspb
+$ ls
+262412 csrdtbs
+73867 vbn
+136389 zqps.hjt
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd nhqwt
+$ ls
+123766 cvcl.jqh
+dir dhrtvctp
+222086 grpdmd.ggz
+dir gzg
+26005 lhpmz.tgz
+dir mcnjwwfr
+117122 msn.gst
+$ cd dhrtvctp
+$ ls
+224079 vdgcqdn.sqd
+$ cd ..
+$ cd gzg
+$ ls
+124395 dqp
+dir wqdbtqm
+$ cd wqdbtqm
+$ ls
+237354 pflp.mdw
+212019 vdgcqdn.sqd
+$ cd ..
+$ cd ..
+$ cd mcnjwwfr
+$ ls
+92504 cshdztf
+dir dctl
+dir dqp
+dir flcrmhlj
+161879 grpdmd.ggz
+dir gtt
+dir hlbnhchz
+220093 mdtdsgvm.zgg
+dir twntr
+287192 vbn
+$ cd dctl
+$ ls
+dir bbhch
+155396 hrrj.jzm
+164971 pblqmwj.vdb
+dir wnlgfpvf
+$ cd bbhch
+$ ls
+dir dpqtp
+dir jvdrcw
+$ cd dpqtp
+$ ls
+174135 gwb.qrb
+$ cd ..
+$ cd jvdrcw
+$ ls
+215993 dcqnblb.cqp
+200800 stjttf.ngc
+$ cd ..
+$ cd ..
+$ cd wnlgfpvf
+$ ls
+135978 cvcl.jqh
+dir dqp
+54018 lbrfmt
+$ cd dqp
+$ ls
+270516 dcqnblb.jqw
+dir dqp
+144626 grpdmd.ggz
+157731 hvcv.rhp
+133773 lnnt
+76250 vdgcqdn.sqd
+$ cd dqp
+$ ls
+41504 zprprf.cmc
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd dqp
+$ ls
+dir dqp
+dir ldzslndn
+236737 mqzcvm.fjh
+239746 nhcdz.ncj
+dir rpchqq
+248824 vdgcqdn.sqd
+250937 zrchht.mwg
+$ cd dqp
+$ ls
+203381 qcq.djm
+$ cd ..
+$ cd ldzslndn
+$ ls
+dir dqp
+dir fptnzlv
+dir gmbnpm
+dir vhvblt
+$ cd dqp
+$ ls
+19579 qcq.lhg
+$ cd ..
+$ cd fptnzlv
+$ ls
+209930 dcqnblb
+$ cd ..
+$ cd gmbnpm
+$ ls
+dir ldzslndn
+dir qcq
+$ cd ldzslndn
+$ ls
+11075 pflp.mdw
+$ cd ..
+$ cd qcq
+$ ls
+dir tdp
+$ cd tdp
+$ ls
+40741 vdgcqdn.sqd
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd vhvblt
+$ ls
+dir lzr
+$ cd lzr
+$ ls
+62245 gbnj.llg
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd rpchqq
+$ ls
+dir bcs
+dir dcqnblb
+dir fvjzn
+dir lrphzrv
+$ cd bcs
+$ ls
+179794 bbn.dzb
+242069 cmjdmzjf.zgf
+1703 cvcl.jqh
+dir gnmhwj
+dir ldzslndn
+152520 qltpsz.jsj
+dir sqqjfps
+$ cd gnmhwj
+$ ls
+dir gvs
+201600 hptn.ftf
+dir hzrnb
+dir qcq
+dir sqhl
+$ cd gvs
+$ ls
+152358 zprprf.mlh
+$ cd ..
+$ cd hzrnb
+$ ls
+94290 gplsfd
+$ cd ..
+$ cd qcq
+$ ls
+91909 vmqd.bmg
+$ cd ..
+$ cd sqhl
+$ ls
+238673 vdgcqdn.sqd
+262885 zmdvr.nfg
+$ cd ..
+$ cd ..
+$ cd ldzslndn
+$ ls
+240461 mdz
+84303 qtj
+$ cd ..
+$ cd sqqjfps
+$ ls
+88753 fwn.tff
+$ cd ..
+$ cd ..
+$ cd dcqnblb
+$ ls
+dir dqp
+189996 dqp.pvp
+$ cd dqp
+$ ls
+dir qvfjz
+196506 vbn
+$ cd qvfjz
+$ ls
+209316 pflp.mdw
+107459 rwpbh.vpt
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd fvjzn
+$ ls
+241464 cvcl.jqh
+dir dqp
+dir ldzslndn
+dir msp
+125 pflp.mdw
+131895 vbn
+$ cd dqp
+$ ls
+34019 pflp.mdw
+202957 vbn
+$ cd ..
+$ cd ldzslndn
+$ ls
+147492 cvcl.jqh
+248719 spc.rfv
+$ cd ..
+$ cd msp
+$ ls
+184407 cvcl.jqh
+$ cd ..
+$ cd ..
+$ cd lrphzrv
+$ ls
+dir bbwqmbg
+81858 cvcl.jqh
+dir dqp
+248670 gqqsww.tsn
+199141 grpdmd.ggz
+dir ldzslndn
+34514 ldzslndn.ctw
+dir tln
+214615 zprprf.fwm
+$ cd bbwqmbg
+$ ls
+129750 flf
+dir pvlw
+dir qcq
+126 sqcqphz.tbm
+$ cd pvlw
+$ ls
+198005 jfvj.hdv
+$ cd ..
+$ cd qcq
+$ ls
+dir wgdzws
+$ cd wgdzws
+$ ls
+253522 ldzslndn.qwt
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd dqp
+$ ls
+281993 cvcl.jqh
+dir hwqjlwcb
+50532 msccz.qgm
+102187 trv.tnq
+111 wplnmj.bfl
+$ cd hwqjlwcb
+$ ls
+267580 dhjqb.dsb
+153195 ldzslndn.jqv
+41526 mvwcwc.zsc
+$ cd ..
+$ cd ..
+$ cd ldzslndn
+$ ls
+58666 cvcl.jqh
+79950 dqp.tmc
+242217 hns.lrb
+dir njswzh
+240692 vdgcqdn.sqd
+dir zvmjvcdm
+52909 zzh
+$ cd njswzh
+$ ls
+149732 cvcl.jqh
+dir rnmfd
+$ cd rnmfd
+$ ls
+75368 dqp.hmv
+14350 vbn
+$ cd ..
+$ cd ..
+$ cd zvmjvcdm
+$ ls
+dir jgczt
+$ cd jgczt
+$ ls
+dir qcq
+95941 qzvvwshv.jwc
+$ cd qcq
+$ ls
+273942 pflp.mdw
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd tln
+$ ls
+dir bmcng
+1518 lrg
+dir vnjfrhp
+$ cd bmcng
+$ ls
+38917 fqcrt
+$ cd ..
+$ cd vnjfrhp
+$ ls
+dir dcqnblb
+dir dqp
+247186 grpdmd.ggz
+dir ldzslndn
+169216 pflp.mdw
+206487 vdgcqdn.sqd
+16976 vlsrzjmb.mmc
+257938 wjl
+$ cd dcqnblb
+$ ls
+dir dqp
+$ cd dqp
+$ ls
+184133 qcq
+$ cd ..
+$ cd ..
+$ cd dqp
+$ ls
+dir dcqnblb
+31612 dqp.pnt
+212283 ldzslndn
+61600 vdbfc.ddj
+197189 wpv.wff
+$ cd dcqnblb
+$ ls
+62412 tfzllmrj
+dir zprprf
+$ cd zprprf
+$ ls
+dir bqnpsl
+dir dszrvpzc
+$ cd bqnpsl
+$ ls
+261548 spbsbbsw.cmn
+$ cd ..
+$ cd dszrvpzc
+$ ls
+188232 sggpqslr.smn
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ldzslndn
+$ ls
+dir bgnhd
+dir pgvcdzwz
+dir qgzhm
+$ cd bgnhd
+$ ls
+56989 cvcl.jqh
+$ cd ..
+$ cd pgvcdzwz
+$ ls
+110034 qhgnndv
+$ cd ..
+$ cd qgzhm
+$ ls
+247232 grpdmd.ggz
+269292 ldzslndn
+153843 tpz
+dir vnschqwr
+162392 wnq.btb
+$ cd vnschqwr
+$ ls
+43005 fvtvzfqm.jvc
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd flcrmhlj
+$ ls
+245668 dcqnblb.sdj
+dir lffj
+229909 pflp.mdw
+280176 vbn
+$ cd lffj
+$ ls
+116451 jmzz.jdd
+dir pjlwb
+162815 pmhlqq.snr
+226183 zffth
+$ cd pjlwb
+$ ls
+67518 qcq.hjq
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd gtt
+$ ls
+52105 grpdmd.ggz
+126869 zprprf.fgj
+$ cd ..
+$ cd hlbnhchz
+$ ls
+3064 dqp.lrw
+278756 grpdmd.ggz
+177208 ldzslndn.wlv
+141685 vbn
+$ cd ..
+$ cd twntr
+$ ls
+63747 cvcl.jqh
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd qcq
+$ ls
+226858 cwblp.zgp
+dir jjqsmfhr
+dir rjbqtrq
+dir vwmpnbts
+141715 wdbhdch
+286381 zprprf
+$ cd jjqsmfhr
+$ ls
+dir btmm
+dir fqndtlgq
+$ cd btmm
+$ ls
+4031 dqp.lrr
+dir fzdd
+$ cd fzdd
+$ ls
+dir vnwpn
+$ cd vnwpn
+$ ls
+dir bzlgsl
+dir ztvzrrbv
+$ cd bzlgsl
+$ ls
+9294 ldzslndn.sqr
+$ cd ..
+$ cd ztvzrrbv
+$ ls
+256017 cvcl.jqh
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd ..
+$ cd fqndtlgq
+$ ls
+271528 ccbmgp.bwd
+$ cd ..
+$ cd ..
+$ cd rjbqtrq
+$ ls
+122150 ldzslndn
+46467 tpdvp.pjf
+$ cd ..
+$ cd vwmpnbts
+$ ls
+47518 fcrwfzvm
+263343 gmc.lrt
+212764 qcq
+$ cd ..
+$ cd ..
+$ cd vwqwlqrt
+$ ls
+dir psrs
+$ cd psrs
+$ ls
+281998 zprprf.hml
+

day_7/lexer.l

@@ -0,0 +1,79 @@
+%{
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "parser.h"
+
+#ifdef DOESNT_HAVE_STRDUP
+#warning DOESNT_HAVE_STRDUP
+char *strdup(const char *s);
+#endif
+
+%}
+
+%option warn nodefault
+
+/* makes the scanner terminate after reaching <<EOF>> instead of assuming a new input was provided */
+%option noyywrap
+/* disable some unused functionality, add scanner tracking */
+%option nounput noinput batch debug
+
+/* gimme a reentrant parser (overkill but more pure) */
+%option reentrant
+
+%option bison-bridge
+
+
+NL                  [\n]
+SPACE               [ ]
+
+/*general definitions*/
+CHAR                [a-zA-Z]
+NUM                 [0-9]
+
+/*operands*/
+SHELL               [$]
+ROOT                [/]
+PARENT              ".."
+CHDIR               "cd"
+LIST                "ls"
+DIR                 "dir"
+
+
+%%
+
+{NL}                { return NEWLINE; }
+{SPACE}             { return SPACE; }
+
+
+{SHELL}{SPACE}      { return PROMPT; }
+{CHDIR}             { return CHDIR; }
+{LIST}              { return LIST; }
+{ROOT}              { return ROOT; }
+{PARENT}            { return PARENT; }
+{DIR}               { return DIRECTORY; }
+
+
+
+{NUM}+              {
+                        unsigned long num = strtoul(yytext, NULL, 10);
+                        yylval->num = num;
+                        return SIZE;
+                    }
+{CHAR}+ |
+{CHAR}+"."{CHAR}+   {
+                        yylval->path = strdup(yytext);
+                        // yylval->path = calloc(strlen(yytext) + 1, sizeof(char));
+                        // strcpy(yylval->path, yytext);
+                        return PATHSPEC;
+                    }
+
+<<EOF>>             {
+                        return END_OF_FILE;
+                    }
+.                   {
+                        printf("[error] Encountered unexpected token %s\n", yytext);
+                        return 0;
+                    }
+
+%%

day_7/parser.y

@@ -0,0 +1,286 @@
+/* Require bison minimal version */
+%require "3.2"
+
+/* write out a header file containing the token defines */
+%header
+
+// Code for the header file generated by bison
+%code requires {
+    #include "filetree.h"
+
+    typedef void* yyscan_t;
+
+    struct dirstack {
+        struct dirstack *next;
+        struct dirnode *item;
+    };
+
+    struct parser_state {
+        struct dirnode *root;
+        struct dirnode *cur;
+
+        /// models the current directory stack we're in for simplicity
+        struct dirstack *stackptr;
+    };
+
+    struct dirstack* dirstack_push(struct dirstack *stack, struct dirnode *item);
+    struct dirstack* dirstack_pop(struct dirstack *stack);
+}
+
+// Code for the c file
+%{
+    #include <stdio.h>
+    #include <stdlib.h>
+    #include <string.h>
+    #include "parser.h"
+    #include "lexer.h"
+
+    const unsigned long upper_bound = 100000;
+    const unsigned long fs_size = 70000000;
+    const unsigned long needed_space = 30000000;
+
+    struct dirstack* dirstack_push(struct dirstack *stack, struct dirnode *item) {
+        struct dirstack *head = calloc(1, sizeof(struct dirstack));
+        if (!head) {
+            fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+            return NULL;
+        }
+
+        head->item = item;
+        head->next = stack;
+
+        return head;
+    }
+
+    struct dirstack* dirstack_pop(struct dirstack *stack) {
+        if (!stack) {
+            fprintf(stderr, "\033[91m[error] Called `dirstack_pop on an empty stack\033[0m\n");
+            return NULL;
+        }
+        
+        struct dirstack *next_item = stack->next;
+        free(stack);
+
+        return next_item;
+    }
+
+    void yyerror(struct parser_state* state, yyscan_t scanner, const char* msg) {
+        (void)state;
+        (void)scanner;
+        fprintf(stderr, "\033[93mSyntax Error: %s\033[0m\n", msg);
+    }
+%}
+
+// define a reentrant parser
+%define api.pure
+
+// enable parser tracing and detailed error messages (plus Lookahead Correction)
+%define parse.trace
+%define parse.error detailed
+%define parse.lac full
+
+%lex-param   { yyscan_t scanner }
+%parse-param { struct parser_state* state }
+%parse-param { yyscan_t scanner }
+
+%union {
+    char *path;
+    unsigned long num;
+}
+
+%start input
+%token NEWLINE SPACE
+%token PROMPT CHDIR LIST
+%token ROOT PARENT DIRECTORY
+%token <path> PATHSPEC
+%token <num> SIZE
+%term END_OF_FILE
+
+%%
+
+input
+    : command input
+    | END_OF_FILE   { return 0; }
+    ;
+
+command
+    : PROMPT CHDIR SPACE ROOT NEWLINE       {
+                                                while (state->stackptr->next) {
+                                                    state->stackptr = dirstack_pop(state->stackptr);
+                                                }
+                                                state->cur = state->stackptr->item;
+                                            }
+    | PROMPT CHDIR SPACE PARENT NEWLINE     {
+                                                state->stackptr = dirstack_pop(state->stackptr);
+                                                state->cur = state->stackptr->item;
+                                            }
+    | PROMPT CHDIR SPACE PATHSPEC NEWLINE   {
+                                                // printf("searching in %s now for path %s\n", state->cur->name, $4);
+                                                    
+                                                // move into the new directory (creating it if it doesn't exist is not necessary, LIST does that)
+                                                struct dirnode *cur_node = state->cur;
+                                                // search for the directory name
+                                                size_t found = 0;
+                                                int c = -1;
+                                                size_t i;
+                                                for (i = 0; i < cur_node->num_dirs; i++) {
+                                                    if (strcmp($4, cur_node->directories[i]->name) == 0) {
+                                                        found = i;
+                                                        c = 0;
+                                                        // printf("equal: [%s] and [%s]\n", $4, cur_node->directories[i]->name);
+                                                    } else {
+                                                        // printf("not equal: [%s] and [%s]\n", $4, cur_node->directories[i]->name);
+                                                    }
+                                                }
+
+                                                if (c == -1) {
+                                                    fprintf(stderr, "\033[91m[error] got no such directory lol\033[0m\n");
+                                                    // TODO: error, directory not found
+                                                } // else {
+                                                    // printf("found it\n");
+                                                // }
+
+                                                struct dirnode *next = cur_node->directories[found];
+
+                                                // actually move into the new directory
+                                                state->stackptr = dirstack_push(state->stackptr, next);
+                                                state->cur = next;
+                                            }
+    | PROMPT LIST NEWLINE output
+    | NEWLINE
+    ;
+
+output
+    : listing NEWLINE output
+    |
+    ;
+
+listing
+    : DIRECTORY SPACE PATHSPEC  {
+                                    struct dirnode *item = calloc(1, sizeof(struct dirnode));
+                                    if (!item) {
+                                        // TODO: error handling
+                                    }
+
+                                    item->name = $3;
+
+                                    add_directory(state->cur, item);
+                                }
+    | SIZE SPACE PATHSPEC       {
+                                    struct filenode *item = calloc(1, sizeof(struct filenode));
+                                    if (!item) {
+                                        // TODO: error handling
+                                    }
+
+                                    item->name = $3;
+                                    item->size = $1;
+
+                                    add_file(state->cur, item);
+                                }
+    ;
+
+%%
+
+
+unsigned long sum_and_count(struct dirnode *node) {
+    unsigned long total_sum = 0;
+
+    for (size_t i = 0; i < node->num_files; i++) {
+        node->size += node->files[i]->size;
+    }
+
+    for (size_t j = 0; j < node->num_dirs; j++) {
+        // recursively call function on subdirectory to compute its size
+        total_sum += sum_and_count(node->directories[j]);
+        node->size += node->directories[j]->size;
+    }
+
+    if (node->size <= upper_bound) {
+        total_sum += node->size;
+    }
+
+    return total_sum;
+}
+
+
+struct dirnode* find_deletion_candidate(struct dirnode *cur, unsigned long needed_space) {
+    if (cur->size < needed_space) {
+        // abort recursion if directory sizes get too small
+        return NULL;
+    }
+
+    struct dirnode *best_candidate = cur;
+    unsigned long best_diff = best_candidate->size - needed_space;
+
+    for (size_t i = 0; i < cur->num_dirs; i++) {
+        struct dirnode *candidate = find_deletion_candidate(cur->directories[i], needed_space);
+        // only proceed if there's an actual candidate
+        if (candidate) {
+            unsigned long delta = candidate->size - needed_space;
+            if (delta < best_diff) {
+                best_candidate = candidate;
+                best_diff = delta;
+            }
+        }
+    }
+
+    return best_candidate;
+}
+
+
+int main(void) {
+    struct dirnode *root = calloc(1, sizeof(struct dirnode));
+    if (!root) {
+        fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+        return EXIT_FAILURE;
+    }
+    root->name = "/\0";
+
+    struct dirstack *stack_ptr = dirstack_push(NULL, root);
+
+    struct parser_state *state = calloc(1, sizeof(struct parser_state));
+    if (!state) {
+        fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+        return EXIT_FAILURE;
+    }
+    state->root = root;
+    state->cur = root;
+    state->stackptr = stack_ptr;
+
+
+    yyscan_t scanner;
+    if (yylex_init(&scanner)) {
+        fprintf(stderr, "\033[91m[error] Could not initialize lexer\033[0m\n");
+        return EXIT_FAILURE;
+    }
+
+    if (yyparse(state, scanner)) {
+		// TODO: Error handling https://www.gnu.org/software/bison/manual/html_node/Parser-Function.html
+		// error during parse occured
+		return EXIT_FAILURE;
+	}
+
+    yylex_destroy(scanner);
+
+    // task 1
+    unsigned long sum_of_sizes = sum_and_count(root);
+    printf("The sum of all directory sizes < %zu is: %zu\n", upper_bound, sum_of_sizes);
+
+    // task 2
+    unsigned long free_space = fs_size - root->size;
+    unsigned long to_clear = needed_space - free_space;
+
+    printf("------------------------------------------------\n");
+    printf("Total Disk Space Available: %zu\n", fs_size);
+    printf("Total Disk Space Used:      %zu\n", root->size);
+    printf("Free Disk Space:            %zu\n", free_space);
+    printf("Required Disk Space:        %zu\n", needed_space);
+    printf("------------------------------------------------\n\n");
+    printf("Looking to free %zu units\n", to_clear);
+
+    struct dirnode *closest_match = find_deletion_candidate(root, to_clear);
+
+    printf("Recommended deletion candidate: `%s` (size %zu)\n", closest_match->name, closest_match->size);
+
+    return 0;
+}

day_8/Makefile

@@ -0,0 +1,3 @@
+TARGET := day_8
+
+include ../Makefile.common.mk

day_8/input.txt

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+

day_8/lexer.l

@@ -0,0 +1,45 @@
+%{
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "parser.h"
+
+%}
+
+%option warn nodefault
+
+/* makes the scanner terminate after reaching <<EOF>> instead of assuming a new input was provided */
+%option noyywrap
+/* disable some unused functionality, add scanner tracking */
+%option nounput noinput batch debug
+
+/* gimme a reentrant parser (overkill but more pure) */
+%option reentrant
+
+%option bison-bridge
+
+
+NL                  [\n]
+
+/*general definitions*/
+NUM                 [0-9]
+
+%%
+
+{NL}                { return NEWLINE; }
+
+{NUM}               {
+                        unsigned long num = strtoul(yytext, NULL, 10);
+                        yylval->num = num;
+                        return NUM;
+                    }
+
+<<EOF>>             {
+                        return END_OF_FILE;
+                    }
+.                   {
+                        printf("[error] Encountered unexpected token %s\n", yytext);
+                        return 0;
+                    }
+
+%%

day_8/parser.y

@@ -0,0 +1,290 @@
+/* Require bison minimal version */
+%require "3.2"
+
+/* write out a header file containing the token defines */
+%header
+
+// Code for the header file generated by bison
+%code requires {
+    typedef void* yyscan_t;
+
+    struct parser_state {
+        /// Layout of the data: forest[row][col]
+        unsigned short **forest;
+        size_t rows;
+        size_t cols;
+
+        unsigned short *current_line;
+        /// for tracking the current position in a line during parsing
+        size_t pos;
+        size_t allocated;
+    };
+}
+
+// Code for the c file
+%{
+    #include <stdio.h>
+    #include <stdlib.h>
+    #include <stdbool.h>
+    #include "parser.h"
+    #include "lexer.h"
+
+    void yyerror(struct parser_state* state, yyscan_t scanner, const char* msg) {
+        (void)state;
+        (void)scanner;
+        fprintf(stderr, "\033[93mSyntax Error: %s\033[0m\n", msg);
+    }
+%}
+
+// define a reentrant parser
+%define api.pure
+
+// enable parser tracing and detailed error messages (plus Lookahead Correction)
+%define parse.trace
+%define parse.error detailed
+%define parse.lac full
+
+%lex-param   { yyscan_t scanner }
+%parse-param { struct parser_state* state }
+%parse-param { yyscan_t scanner }
+
+%union {
+    unsigned long num;
+}
+
+%start input
+%token NEWLINE
+%token <num> NUM
+%term END_OF_FILE
+
+%%
+
+input
+    : treerow input
+    | END_OF_FILE   { return 0; }
+    ;
+
+treerow
+    : NUM treerow   {
+                        if (state->pos >= state->allocated) {
+                            state->allocated += 10;
+                            state->current_line = realloc(state->current_line, state->allocated * sizeof(unsigned short));
+                            if (!state->current_line) {
+                                fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+                                YYABORT;
+                            }
+                        }
+
+                        state->current_line[state->pos] = $1;
+                        state->pos++;
+                    }
+    | NEWLINE       {
+                        if (state->pos != 0) {
+                            state->forest = realloc(state->forest, (state->rows + 1) * sizeof(unsigned short *));
+                            if (!state->forest) {
+                                fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+                                YYABORT;
+                            }
+
+                            // resize the current line if necessary
+                            if (state->allocated > state->pos) {
+                                state->current_line = realloc(state->current_line, state->pos * sizeof(unsigned short));
+                                // cannot really fail but oh well
+                                if (!state->current_line) {
+                                    fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+                                    YYABORT;
+                                }
+                            }
+
+                            if (state->pos != state->cols) {
+                                if (state->cols != 0) {
+                                    fprintf(stderr, "\033[91m[error] Column size has changed mid-parse\033[0m\n");
+                                    YYERROR;
+                                }
+
+                                state->cols = state->pos;
+                            }
+
+                            // write the current line to the forest
+                            state->forest[state->rows] = state->current_line;
+                            state->rows++;
+
+                            // initialize a new row
+                            state->allocated = state->cols;
+                            state->pos = 0;
+                            state->current_line = calloc(state->allocated, sizeof(unsigned short));
+
+                            if (!state->current_line) {
+                                fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+                                YYABORT;
+                            }
+                        }
+                    }
+    ;
+
+
+%%
+
+
+unsigned long compute_scenic_score(struct parser_state *state, size_t row, size_t col) {
+    unsigned short height = state->forest[row][col];
+
+    unsigned long up = 0;
+    for (int r = row - 1; r >= 0; r--) {
+        up++;
+        if (state->forest[r][col] >= height) {
+            break;
+        }
+    }
+
+    unsigned long down = 0;
+    for (size_t r = row + 1; r < state->rows; r++) {
+        down++;
+        if (state->forest[r][col] >= height) {
+            break;
+        }
+    }
+
+    unsigned long left = 0;
+    for (int c = col - 1; c >= 0; c--) {
+        left++;
+        if (state->forest[row][c] >= height) {
+            break;
+        }
+    }
+
+    unsigned long right = 0;
+    for (size_t c = col + 1; c < state->cols; c++) {
+        right++;
+        if (state->forest[row][c] >= height) {
+            break;
+        }
+    }
+
+    return up * down * left * right;
+}
+
+int main(void) {
+    struct parser_state *state = calloc(1, sizeof(struct parser_state));
+    if (!state) {
+        fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+        return EXIT_FAILURE;
+    }
+    state->allocated = 100;
+    state->current_line = calloc(state->allocated, sizeof(unsigned short));
+    if (!state->current_line) {
+        fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+        return EXIT_FAILURE;
+    }
+
+    yyscan_t scanner;
+    if (yylex_init(&scanner)) {
+        fprintf(stderr, "\033[91m[error] Could not initialize lexer\033[0m\n");
+        return EXIT_FAILURE;
+    }
+
+    if (yyparse(state, scanner)) {
+		// TODO: Error handling https://www.gnu.org/software/bison/manual/html_node/Parser-Function.html
+		// error during parse occured
+		return EXIT_FAILURE;
+	}
+
+    yylex_destroy(scanner);
+
+    // task 1
+    // create a bitmap marking counted visible trees
+    bool **bitmap = calloc(state->rows, sizeof(bool *));
+    if (!bitmap) {
+        fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+        return EXIT_FAILURE;
+    }
+    for (size_t i = 0; i < state->rows; i++) {
+        bitmap[i] = calloc(state->cols, sizeof(bool));
+        if (!bitmap[i]) {
+            fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+            return EXIT_FAILURE;
+        }
+    }
+
+    // count all outer rows and cols as visible
+    unsigned long visible = 0;
+
+    for (size_t c = 0; c < state->cols; c++) {
+        unsigned short tallest = state->forest[0][c];
+        bitmap[0][c] = true;
+        visible++;
+        // top->down
+        for (size_t r = 0; r < (state->rows - 1); r++) {
+            if (state->forest[r][c] > tallest) {
+                tallest = state->forest[r][c];
+                if (!bitmap[r][c]) {
+                    visible++;
+                    bitmap[r][c] = true;
+                }
+            }
+        }
+        // bottom->up
+        tallest = state->forest[state->rows - 1][c];
+        visible++;
+        bitmap[state->rows - 1][c] = true;
+        for (size_t r = state->rows - 1; r > 0; r--) {
+            if (state->forest[r][c] > tallest) {
+                tallest = state->forest[r][c];
+                if (!bitmap[r][c]) {
+                    visible++;
+                    bitmap[r][c] = true;
+                }
+            }
+        }
+    }
+
+    // move through individual rows
+    for (size_t r = 0; r < state->rows; r++) {
+        unsigned short tallest = state->forest[r][0];
+        if (!bitmap[r][0]) {
+            bitmap[r][0] = true;
+            visible++;
+        }
+        // left->right
+        for (size_t c = 0; c < (state->cols - 1); c++) {
+            if (state->forest[r][c] > tallest) {
+                tallest = state->forest[r][c];
+                if (!bitmap[r][c]) {
+                    visible++;
+                    bitmap[r][c] = true;
+                }
+            }
+        }
+        // right->left
+        tallest = state->forest[r][state->cols - 1];
+        if (!bitmap[r][state->cols - 1]) {
+            bitmap[r][state->cols - 1] = true;
+            visible++;
+        }
+        for (size_t c = state->cols - 1; c > 0; c--) {
+            if (state->forest[r][c] > tallest) {
+                tallest = state->forest[r][c];
+                if (!bitmap[r][c]) {
+                    visible++;
+                    bitmap[r][c] = true;
+                }
+            }
+        }
+    }
+
+    printf("Visible trees: %zu\n", visible);
+
+    unsigned long best = 0;
+    for (size_t r = 0; r < state->rows; r++) {
+        for (size_t c = 0; c < state->cols; c++) {
+            unsigned long tmp = compute_scenic_score(state, r, c);
+            if (tmp > best) {
+                best = tmp;
+            }
+        }
+    }
+
+    printf("Best scenic score: %zu\n", best);
+
+    return 0;
+}

day_9/Makefile

@@ -0,0 +1,3 @@
+TARGET := day_9
+
+include ../Makefile.common.mk

day_9/lexer.l

@@ -0,0 +1,56 @@
+%{
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "parser.h"
+
+%}
+
+%option warn nodefault
+
+/* makes the scanner terminate after reaching <<EOF>> instead of assuming a new input was provided */
+%option noyywrap
+/* disable some unused functionality, add scanner tracking */
+%option nounput noinput batch debug
+
+/* gimme a reentrant parser (overkill but more pure) */
+%option reentrant
+
+%option bison-bridge
+
+
+NL                  [\n]
+SPACE               " "
+
+DOWN                "D"
+UP                  "U"
+LEFT                "L"
+RIGHT               "R"
+
+/*general definitions*/
+NUM                 [0-9]
+
+%%
+
+{NL}                { return NEWLINE; }
+{SPACE}             { /* return SPACE; */ }
+{DOWN}              { return DOWN; }
+{UP}                { return UP; }
+{LEFT}              { return LEFT; }
+{RIGHT}             { return RIGHT; }
+
+{NUM}+              {
+                        unsigned long num = strtoul(yytext, NULL, 10);
+                        yylval->num = num;
+                        return NUM;
+                    }
+
+<<EOF>>             {
+                        return END_OF_FILE;
+                    }
+.                   {
+                        printf("[error] Encountered unexpected token %s\n", yytext);
+                        return 0;
+                    }
+
+%%

day_9/parser.y

@@ -0,0 +1,172 @@
+/* Require bison minimal version */
+%require "3.2"
+
+/* write out a header file containing the token defines */
+%header
+
+// Code for the header file generated by bison
+%code requires {
+    #include <stdbool.h>
+
+    #define MAX_X 500
+    #define MAX_Y 500
+
+    typedef void* yyscan_t;
+
+    struct parser_state {
+        bool field[MAX_X][MAX_Y];
+
+        size_t head_x;
+        size_t head_y;
+        size_t tail_x;
+        size_t tail_y;
+
+        unsigned long visited;
+    };
+}
+
+// Code for the c file
+%{
+    #include <stdio.h>
+    #include <stdlib.h>
+    #include "parser.h"
+    #include "lexer.h"
+
+    void yyerror(struct parser_state* state, yyscan_t scanner, const char* msg) {
+        (void)state;
+        (void)scanner;
+        fprintf(stderr, "\033[93mSyntax Error: %s\033[0m\n", msg);
+    }
+%}
+
+// define a reentrant parser
+%define api.pure
+
+// enable parser tracing and detailed error messages (plus Lookahead Correction)
+%define parse.trace
+%define parse.error detailed
+%define parse.lac full
+
+%lex-param   { yyscan_t scanner }
+%parse-param { struct parser_state* state }
+%parse-param { yyscan_t scanner }
+
+%union {
+    unsigned long num;
+}
+
+%start input
+%token NEWLINE
+%token DOWN UP LEFT RIGHT
+%token <num> NUM
+%term END_OF_FILE
+
+%%
+
+input
+    : line input
+    | END_OF_FILE   { return 0; }
+    ;
+
+line
+    : movement NEWLINE
+    | NEWLINE
+    ;
+
+movement
+    : UP NUM    {
+                    for (size_t i = 0; i < $2; i++) {
+                        state->head_y++;
+                        if ((state->head_y - state->tail_y) > 1) {
+                            state->tail_y = state->head_y - 1;
+                            state->tail_x = state->head_x;
+                        }
+
+                        if (!state->field[state->tail_x][state->tail_y]) {
+                            state->field[state->tail_x][state->tail_y] = true;
+                            state->visited++;
+                        }
+                    }
+                }
+    | DOWN NUM  {
+                    for (size_t i = 0; i < $2; i++) {
+                        state->head_y--;
+                        if ((state->tail_y - state->head_y) > 1) {
+                            state->tail_y = state->head_y + 1;
+                            state->tail_x = state->head_x;
+                        }
+
+                        if (!state->field[state->tail_x][state->tail_y]) {
+                            state->field[state->tail_x][state->tail_y] = true;
+                            state->visited++;
+                        }
+                    }
+                }
+    | RIGHT NUM {
+                    for (size_t i = 0; i < $2; i++) {
+                        state->head_x++;
+                        if ((state->head_x - state->tail_x) > 1) {
+                            state->tail_x = state->head_x - 1;
+                            state->tail_y = state->head_y;
+                        }
+
+                        if (!state->field[state->tail_x][state->tail_y]) {
+                            state->field[state->tail_x][state->tail_y] = true;
+                            state->visited++;
+                        }
+                    }
+                }
+    | LEFT NUM  {
+                    for (size_t i = 0; i < $2; i++) {
+                        state->head_x--;
+                        if ((state->tail_x - state->head_x) > 1) {
+                            state->tail_x = state->head_x + 1;
+                            state->tail_y = state->head_y;
+                        }
+
+                        if (!state->field[state->tail_x][state->tail_y]) {
+                            state->field[state->tail_x][state->tail_y] = true;
+                            state->visited++;
+                        }
+                    }
+                }
+    ;
+
+
+%%
+
+
+int main(void) {
+    struct parser_state *state = calloc(1, sizeof(struct parser_state));
+    if (!state) {
+        fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
+        return EXIT_FAILURE;
+    }
+
+    state->head_x = MAX_X / 2;
+    state->head_y = MAX_Y / 2;
+    state->tail_x = MAX_X / 2;
+    state->tail_y = MAX_Y / 2;
+
+    state->visited = 1; // the starting position
+    state->field[state->tail_x][state->tail_y] = true;
+
+    yyscan_t scanner;
+    if (yylex_init(&scanner)) {
+        fprintf(stderr, "\033[91m[error] Could not initialize lexer\033[0m\n");
+        return EXIT_FAILURE;
+    }
+
+    if (yyparse(state, scanner)) {
+		// TODO: Error handling https://www.gnu.org/software/bison/manual/html_node/Parser-Function.html
+		// error during parse occured
+		return EXIT_FAILURE;
+	}
+
+    yylex_destroy(scanner);
+
+    // task 1
+    printf("Visited nodes: %zu\n", state->visited);
+
+    return 0;
+}

shell.nix

@@ -0,0 +1,11 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  propagatedNativeBuildInputs = with pkgs; [
+    flex
+    bison
+    clang
+  ];
+
+}
+