AoC18/day3p1/main.c

#include <stdio.h>

#include <glib.h>

struct claim {
    unsigned id;
    unsigned x;
    unsigned y;
    unsigned w;
    unsigned h;
};

struct claim *parseclaims(unsigned *len, const char *fname)
{
    FILE *f = fopen(fname, "r");
    if (!f) {
        perror(fname);
        return NULL;
    }

    GArray *array = g_array_new(FALSE, FALSE, sizeof(struct claim));
    *len = 0;

    char *line = NULL;
    size_t line_len = 0;
    while (getline(&line, &line_len, f) != -1) {
        struct claim claim = {0};

        // Haha what is proper parsing
        sscanf(line, "#%u @ %u,%u: %ux%u",
                &claim.id,
                &claim.x,
                &claim.y,
                &claim.w,
                &claim.h
        );

        g_array_append_val(array, claim);
        (*len)++;
    }

    free(line);
    fclose(f);
    struct claim *res = (struct claim *)g_array_free(array, FALSE);
    return res;
}

int main()
{
    unsigned claims_len;
    struct claim *claims = parseclaims(&claims_len, "input");
    if (!claims) return 1;

    char (*tilemap)[1000] = g_malloc0(sizeof(char[1000][1000]));

    for (struct claim *claim = claims;
            claim < claims + claims_len; claim++) {
        // Basic sanity check
        if (claim->y > 1000 ||
                claim->y + claim->h > 1000 ||
                claim->x > 1000 ||
                claim->x + claim->w > 1000) {
            fprintf(stderr, "Warning: Ignoring out-of-bounds claim: "
                    "#%u @ %u,%u: %ux%u\n",
                    claim->id,
                    claim->x,
                    claim->y,
                    claim->w,
                    claim->h
            );
            continue;
        }

        for (unsigned y = claim->y; y < claim->y + claim->h; y++) {
            for (unsigned x = claim->x; x < claim->x + claim->w; x++) {
                if (tilemap[y][x] >= 2) continue;
                tilemap[y][x]++;
            }
        }
    }

    int tally = 0;
    for (char *i = *tilemap; i < *tilemap + 1000 * 1000; i++) {
        if (*i >= 2) tally++;
    }

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

    g_free(claims);
    g_free(tilemap);
    return 0;
}