advent-of-code

day04_01.c (4605B)

---

 #if 0
 # Self-building c file. Invoke like: `./file.c`
 outdir=out
 input=$(basename "$0")
 output="$outdir"/$(basename "$0" .c)
 if [ "$input" -nt "$output" ];
 then
     mkdir --parents "$outdir" || exit
     echo "Building ${output}." || exit
     clang -std=c11 -Wall -Wextra -pedantic -Wno-unused-function -I../../amlibs/ "$input" -o "$output" || exit
 fi
 if [ "$1" = "-r" ];
 then
     ./"$output" "$@"
 fi
 exit
 #endif
 
 #include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 _Noreturn void assert_fail(const char *expr, const char *file, int line, const char *func) {
     fprintf(stderr, "%s:%d: %s: Assertion failed: '%s'\n", file, line, func, expr);
     abort();
 }
 
 #define AM_ENABLE_ASSERT 1
 #define AM_ASSERT_FAIL(expr, file, line, func) assert_fail(expr, file, line, func)
 #include "am_base.h"
 #include "am_memory.h"
 #include "am_list.h"
 #include "am_string.h"
 
 Str open_file(MemArena *arena, char *path) {
     FILE *f = fopen(path, "r");
     assert(f);
 
     s32 error = fseek(f, 0L, SEEK_END);
     assert(!error);
 
     s64 size = ftell(f);
     assert(size >= 0);
     rewind(f);
 
     u8 *buf = am_mem_arena_push(arena, size);
     assert(buf);
 
     size_t items_read = fread(buf, 1, size, f);
     assert(items_read == (size_t)size);
 
     error = fclose(f);
     assert(!error);
 
     return am_str(buf, size);
 }
 
 int compare_u64(const void *a, const void *b) {
     u64 num_a = *((u64 *)a);
     u64 num_b = *((u64 *)b);
     if (num_a == num_b) {
         return 0;
     } else if (num_a < num_b) {
         return -1;
     } else {
         return 1;
     }
 }
 
 s64 parse_number(Str s) {
     s64 number = 0;
     for (u64 i = 0; i < s.size; i++) {
         assert(s.str[i] >= '0' && s.str[i] <= '9');
         number = (number * 10) + (s.str[i] - '0');
     }
     return number;
 }
 
 int main(void) {
     MemArena a = am_mem_arena_create(am_mem_base_allocator_malloc());
     Str input = open_file(&a, "day04_input.txt");
 
     StrList split_data = am_str_split(&a, input, (u8 *)"\n ", 2);
     am_str_list_discard_empty(&split_data);
     StrList split_first_line = am_str_split(&a, split_data.first->s, (u8 *)",", 1);
 
     u64 drawn_number_count = split_first_line.node_count;
     u64 board_number_count = split_data.node_count - 1;
     assert(board_number_count % 25 == 0);
 
     s64 *drawn_numbers = AM_MEM_ARENA_PUSH_ARRAY(&a, s64, drawn_number_count);
     s64 *board_numbers = AM_MEM_ARENA_PUSH_ARRAY(&a, s64, board_number_count);
 
     {
         u64 i = 0;
         for (StrListNode *number = split_first_line.first; number; number = number->next) {
             drawn_numbers[i] = parse_number(number->s);
             i++;
         }
         assert(i == drawn_number_count);
     }
 
     {
         u64 i = 0;
         for (StrListNode *number = split_data.first->next; number; number = number->next) {
             board_numbers[i] = parse_number(number->s);
             i++;
         }
         assert(i == board_number_count);
     }
 
     bool game_won = false;
     u64 winning_score = 0;
 
     for (u64 drawn_i = 0; drawn_i < drawn_number_count; drawn_i++) {
         s64 drawn = drawn_numbers[drawn_i];
 
         for (u64 board_i = 0; board_i < board_number_count; board_i++) {
             if (board_numbers[board_i] == drawn) {
                 board_numbers[board_i] = -1;
             }
         }
 
         u8 row_count = 0;
         u8 col_count[5] = {0};
         for (u64 board_i = 0; board_i < board_number_count; board_i++) {
             u64 board = board_i / 25;
             u64 cell = board_i % 25;
             u64 row = cell / 5;
             u64 col = cell % 5;
 
             row_count      += board_numbers[board_i] == -1;
             col_count[col] += board_numbers[board_i] == -1;
 
             if ((cell + 1) / 5 != row) {
                 if (row_count == 5) {
                     game_won = true;
                 } else {
                     row_count = 0;
                 }
             }
 
             if (row == 4) {
                 if (col_count[col] == 5) {
                     game_won = true;
                 } else {
                     col_count[col] = 0;
                 }
             }
 
             if (game_won) {
                 for (u64 i = board * 25; i < board * 25 + 25; i++) {
                     winning_score += board_numbers[i] * (board_numbers[i] != -1);
                 }
                 winning_score *= drawn;
                 goto game_over;
             }
         }
     }
 
 game_over:
     if (game_won) {
         printf("Winning score: %" PRIu64 "\n", winning_score);
     } else {
         printf("No Winning Board!\n");
     }
 
     am_mem_arena_release(&a);
     return 0;
 }