aoc2025/day5.c

#include "lib.h"
#include <stdlib.h>

#define DBG 0
#define PRETTY 1

static
unsigned char input[] = {
#embed "day5_input.txt"
};

static
unsigned char test[] = {
#embed "day5_test.txt"
};

#if PRETTY
struct line {
    union {
        unsigned char l[64];
        struct {
            unsigned char s[16];
            unsigned char pad0[4];
            unsigned char e[16];
            unsigned char pad1[4];
            num sv;
            num ev;
        };
    };
};
static_assert(sizeof(struct line) == 0x40);
#else
struct line {
    num sv;
    num ev;
};
#endif

alignas(0x40) static
struct line ranges[256];

static
int linecmp(const void *av, const void *bv) {
    const struct line *a = av;
    const struct line *b = bv;
    if (a->sv < b->sv) return -1;
    else if (a->sv > b->sv) return 1;
    else return 0;
}

static
unsigned long do_part1(size_t file_len, unsigned char file[file_len]) {
    unsigned char *s = file;
    unsigned long result = 0;

    memset(ranges, 0, sizeof(ranges));

#if DBG
    print("\n");
#endif

    struct line *d = ranges;
    do {
        unsigned char *tmp;
        d->sv = grabbcd(s, &tmp);
#if PRETTY
        memcpy(d->s, s, tmp - s);
#endif
        s = tmp;
        s++;
        d->ev = grabbcd(s, &tmp);
#if PRETTY
        memcpy(d->e, s, tmp - s);
#endif
        s = tmp;
        s++;
        d++;
    } while (*s != '\n');

#if PRETTY
    size_t range_cnt = d - ranges;
    qsort(ranges, range_cnt, sizeof(*ranges), linecmp);
#endif

    d->sv = 0;
    s++;

    do {
        bcdint id = grabbcd(s, &s);
        for (d = ranges; d->sv; d++) {
            bcdint ds = d->sv;
            bcdint de = d->ev;
            if (id >= ds && id <= de) {
                result++;
                goto next_id;
            }
        }
next_id:
        s++;
    } while (s != &file[file_len]);

    return result;
}

static
unsigned long do_part2(size_t file_len, unsigned char file[file_len]) {
    unsigned char *s = file;
    unsigned long result = 0;

    memset(ranges, 0, sizeof(ranges));

#if DBG
    print("\n");
#endif

    struct line *d = ranges;
    do {
        unsigned char *tmp;
        d->sv = grabbcd(s, &tmp);
#if PRETTY
        snprinth(d->sv, sizeof(d->s), d->s);
#endif
        s = tmp;
        s++;
        d->ev = grabbcd(s, &tmp);
#if PRETTY
        snprinth(d->ev, sizeof(d->e), d->e);
#endif
        s = tmp;
        s++;
        d++;
    } while (*s != '\n');

#if PRETTY
    size_t range_cnt = d - ranges;
    qsort(ranges, range_cnt, sizeof(*ranges), linecmp);
#endif

    d->sv = 0;

    outer:
    for (struct line *di = ranges; di->sv; di++) {
        bcdint dis = di->sv;
        bcdint die = di->ev;
        if (dis == -1) continue;
        for (struct line *dj = di+1; dj->sv; dj++) {
            bcdint djs = dj->sv;
            bcdint dje = dj->ev;
            if (djs == -1) continue;
            if (djs <= die && djs >= dis) {
                djs = bcdadd(die, 1);
            }
            if (dje >= dis && dje <= die) {
                dje = bcdsub(dis, 1);
            }
            if (djs == dj->sv && dje == dj->ev)
                continue;
            if (dje < djs) {
#if DBG
                print("FOR: "); printd(dis); print(" "); printd(die); print("\n");
                print("     "); printd(dj->sv); print(" "); printd(dj->ev); print("\n");
                print("  -> "); printd(djs); print(" "); printd(dje); print(" BAD\n");
#endif
                dj->sv = -1;
                dj->ev = -1;
#if PRETTY
                snprinth(dj->sv, sizeof(dj->s), dj->s);
                snprinth(dj->ev, sizeof(dj->e), dj->e);
#endif
            } else {
#if DBG
                print("FOR: "); printd(dis); print(" "); printd(die); print("\n");
                print("     "); printd(dj->sv); print(" "); printd(dj->ev); print("\n");
                print("  -> "); printd(djs); print(" "); printd(dje); print("\n");
#endif
                dj->sv = djs;
                dj->ev = dje;
#if PRETTY
                snprinth(dj->sv, sizeof(dj->s), dj->s);
                snprinth(dj->ev, sizeof(dj->e), dj->e);
#endif
            }
        }
    }

    for (struct line *di = ranges; di->sv; di++) {
        if (di->sv == -1) continue;
        unsigned long dis = bcdtonum(di->sv);
        unsigned long die = bcdtonum(di->ev);
        result += die - dis + 1;
    }

    return result;
}

#define RUN_TEST1 1
#define RUN_PART1 1
#define RUN_TEST2 1
#define RUN_PART2 1

#define TEST1_EXPECT 3
#define TEST2_EXPECT 14

void run() {
#if RUN_TEST1
    print("PART 1 TEST: ");
    if (unsigned long v = do_part1(countof(test), test); v != TEST1_EXPECT) {
        print("FAILED (got ");
        printd(v);
        print(", expected " xstr(TEST1_EXPECT) ")\n");
    } else {
        print("PASSED\n");
    }
#endif

#if RUN_PART1
    print("PART 1 RESULT: ");
    printd(do_part1(countof(input), input));
    print("\n");
#endif

#if RUN_TEST2
    print("PART 2 TEST: ");
    if (unsigned long v = do_part2(countof(test), test); v != TEST2_EXPECT) {
        print("FAILED (got ");
        printd(v);
        print(", expected " xstr(TEST2_EXPECT) ")\n");
    } else {
        print("PASSED\n");
    }
#endif

#if RUN_PART2
    print("PART 2 RESULT: ");
    printd(do_part2(countof(input), input));
    print("\n");
#endif

    exit_group(0);
}