aoc2023/day2/p1.c

#define  _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>


uint64_t parse_number(char *end);

#define SETS_STR_MAX_LEN 200

#define CUBE_RED_MAX 12
#define CUBE_GREEN_MAX 13
#define CUBE_BLUE_MAX 14


int main(int argc, char **argv) {
    FILE *input;
    char *line = NULL;
    size_t line_length = 0;

    if (argc == 1 || argv[1][0] == '-')
		input = stdin;
	else if ((input = fopen(argv[1], "r")) == NULL) {
		fprintf(stderr, "Cannot open file %s\n", argv[1]);
		return -1;
	}

    int32_t game_id_sum = 0;

    while (getline(&line, &line_length, input) != -1) {
        char *colon_pos = strchr(line, ':');

        int32_t game_id = parse_number(colon_pos - 1);
        bool is_correct = true;

        char *sets = colon_pos + 2;
        char *space_pos = NULL;

        while (NULL != (space_pos = strchr(sets, ' '))) {
            if (*(space_pos-1) == ',' || *(space_pos-1) == ';') {
                sets = space_pos + 1;
                continue;
            }

            int8_t n = parse_number(space_pos-1);

            if (('r' == *(space_pos+1) && CUBE_RED_MAX < n) ||
                ('g' == *(space_pos+1) && CUBE_GREEN_MAX < n) ||
                ('b' == *(space_pos+1) && CUBE_BLUE_MAX < n)) {
                is_correct = false;
                break;
            }

            sets = space_pos + 1;
        }

        if (is_correct)
            game_id_sum += game_id;

        memset(line, 0, line_length);
    }

    printf("%d\n", game_id_sum);

    return 0;
}

uint64_t parse_number(char *end) {
    uint64_t num = 0;

    for (size_t n = 1;; n *= 10) {
        if (*end>>4 != 0x3)
            break;
        num += (*end&0xf) * n;
        --end;
    }

    return num;
}