advent-of-code-2023/day2/part1.c

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <regex.h>
#include <string.h>

typedef struct elfgame {
    long number; 
    struct elfgame_play *plays;
    struct elfgame *next;
} elfgame;

typedef struct elfgame_play {
    long red, blue, green;
    struct elfgame_play *next;
} elfgame_play;

elfgame *first_game;

void read_line(char* linebuf, FILE* file) 
{
    char* str = fgets(linebuf, 2048, file);
    if (feof(file))
    {
        return;
    }
    if (str == NULL)
    {
        fprintf(stderr, "Fgets error");
        linebuf[0] = '\0';
    }
}

long get_gamenum(char* line)
{
    regex_t regex;
    char pattern[] = "Game ([0-9]+):.*";
    regmatch_t pmatch[2];
    if (regcomp(&regex, pattern, REG_EXTENDED))
    {
        fprintf(stderr, "error compiling regex");
        return -1;
    }
    int rc = regexec(&regex, line, 2, pmatch, 0);
    if (rc)
    {
        char buf[2048];
        regerror(rc, &regex, buf, 2048);
        fprintf(stderr, "error execing regex");
        return -1;
    }
    return strtoul(line + pmatch[1].rm_so, NULL, 10);
}

elfgame_play *parse_play(char *line, int offset)
{
    regex_t regex;
    regmatch_t pmatch[3];
    char pattern[] =  "([0-9]+)[[:space:]](red|green|blue);?";
    char *s = line;
    elfgame_play *p = malloc(sizeof(elfgame_play));
    if (p == NULL)
    {
        fprintf(stderr, "OOM");
        return NULL;
    }
    p->red = p->blue = p->green = 0;
    if (regcomp(&regex, pattern, REG_EXTENDED))
    {
        fprintf(stderr, "error compiling regex");
        return NULL;
    }
    for (int i = 0; ; i++)
    {
        if (regexec(&regex, s, 3, pmatch, 0))
            break;
        if (s >= line + offset)
            break;
        long count = strtoul(s + pmatch[1].rm_so, NULL, 10);
        if (strncmp(s + pmatch[2].rm_so, "red", 3) == 0)
        {
            p->red += count;
        }
        if (strncmp(s + pmatch[2].rm_so, "blue", 4) == 0)
        {
            p->blue += count;
        }
        if (strncmp(s + pmatch[2].rm_so, "green", 5) == 0)
        {
            p->green += count;
        }
        s += pmatch[0].rm_eo;
    }
    regfree(&regex);
    return p;
}

elfgame_play *parse_plays(char* line, int offset)
{
    regex_t regex;
    regmatch_t pmatch[3];
    char pattern[] =  "([0-9]+)[[:space:]](red|blue|green)";
    char *s = line;
    elfgame_play *first = malloc(sizeof(elfgame_play));
    if (first == NULL)
    {
        fprintf(stderr, "OOM");
        return NULL;
    }
    elfgame_play *cur = first;
    if (regcomp(&regex, pattern, REG_EXTENDED))
    {
        fprintf(stderr, "error compiling regex");
        return NULL;
    }
    for (int i = 0; ; i++)
    {
        if (regexec(&regex, s, 3, pmatch, 0))
            break;
        if (s > line + offset)
            break;
        elfgame_play *p = malloc(sizeof(elfgame_play));
        if (p == NULL)
        {
            fprintf(stderr, "OOM");
            return NULL;
        }
        p->red = p->blue = p->green = 0;
        long count = strtoul(s + pmatch[1].rm_so, NULL, 10);
        if (strncmp(s + pmatch[2].rm_so, "red", 3) == 0)
        {
            p->red += count;
        }
        if (strncmp(s + pmatch[2].rm_so, "blue", 4) == 0)
        {
            p->blue += count;
        }
        if (strncmp(s + pmatch[2].rm_so, "green", 5) == 0)
        {
            p->green += count;
        }
        cur->next = p;
        cur = cur->next;
        s += pmatch[0].rm_eo;
    }
    return first; 
}

elfgame *parse_game(char* line)
{
    regex_t regex;
    regmatch_t pmatch[4];
    char pattern[] = "(([0-9]+)[[:space:]](red|blue|green),?[[:space:]]?)+;?";
    if (regcomp(&regex, pattern, REG_EXTENDED))
    {
        fprintf(stderr, "error compiling regex");
        return NULL;
    }
    char *s = line;
    elfgame *g = malloc(sizeof(elfgame));
    if (g == NULL)
    {
        return NULL;
    }
    g->number = get_gamenum(line); 
    elfgame_play *dummy = malloc(sizeof(elfgame_play));
    if (dummy == NULL)
    {
        return NULL;
    }
    dummy->red = dummy->green = dummy->blue = 0;
    elfgame_play *cur = dummy;
    g->plays = dummy;
    for (int i = 0; ; i++)
    {
        if(regexec(&regex, s, 4, pmatch, 0))
            break;
        cur->next = parse_play(line, pmatch[0].rm_eo);
        cur = cur->next;
        s += pmatch[0].rm_eo;
    }
    regfree(&regex);
    return g;
}

int main(int argc, char *argv[])
{
    char buffer[2048];
    FILE* input = fopen("input", "r"); 
    if (input == NULL)
    {
        fprintf(stderr, "error opening file");
        return EXIT_FAILURE;
    }
    long sum = 0;
    first_game = malloc(sizeof(elfgame));
    if (first_game == NULL)
    {
        fprintf(stderr, "OOM");
        return EXIT_FAILURE;
    }
    elfgame *cur = first_game;
    while(true)
    {
        read_line(buffer, input);
        if (feof(input))
            break;
        elfgame *g = parse_game(buffer);
        cur->next = g;
        cur = cur->next;
    }

    printf("%ld", sum);
    return EXIT_SUCCESS;
}