diff --git a/day_8/Makefile b/day_8/Makefile new file mode 100644 index 0000000..b341111 --- /dev/null +++ b/day_8/Makefile @@ -0,0 +1,3 @@ +TARGET := day_8 + +include ../Makefile.common.mk diff --git a/day_8/input.txt b/day_8/input.txt new file mode 100644 index 0000000..a68f5c1 --- /dev/null +++ b/day_8/input.txt @@ -0,0 +1,100 @@ +102212110110302230012132130441442043243242145112422525112333344240121120342411110001231112222021211 +222101001302011022124443303121322323142224235123233315215333545242421321241403143213333101310210211 +200201223122002022301310313414224443253123231515151513541254251131310343344222040320023211301320200 +200010213032223103230132143412204353411323525332513442523314324332413034422122304413120211230122212 +010211000332000340422300132032513533513115523254315325423242433353351244232123121111220123121333221 +200122303232310323111312343413321244422555551325423211253434511531321144403333313021201212232131220 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yylval->num = num; + return NUM; + } + +<> { + return END_OF_FILE; + } +. { + printf("[error] Encountered unexpected token %s\n", yytext); + return 0; + } + +%% diff --git a/day_8/parser.y b/day_8/parser.y new file mode 100644 index 0000000..4ebb25e --- /dev/null +++ b/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 + #include + #include + #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 +%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; +}