solve task 2, day 5

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"
 
@@ -115,6 +120,25 @@ 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);
+
+        if (state->is_gen_two) {
+            struct stack_item* it = state->stacks[$4 - 1];
+            for (unsigned long i = 1; i < $2; i++) {
+                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;
+            }
+
+            struct stack_item* tmp = state->stacks[$4 - 1];
+            state->stacks[$4 - 1] = it->next;
+
+            it->next = state->stacks[$6 - 1];
+            state->stacks[$6 - 1] = tmp;
+        } else {
             for (unsigned long i = 0; i < $2; i++) {
                 // get the current element
                 struct stack_item* it = state->stacks[$4 -1];
@@ -133,14 +157,21 @@ expr
                 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");