AoC18/day16p2/main.c

#include <stdlib.h>
#include <stdio.h>

#include <glib.h>

#define REGS 4

typedef long reg_t;

enum instr_id {
    INSTR_ADDR,
    INSTR_ADDI,
    INSTR_MULR,
    INSTR_MULI,
    INSTR_BANR,
    INSTR_BANI,
    INSTR_BORR,
    INSTR_BORI,
    INSTR_SETR,
    INSTR_SETI,
    INSTR_GTIR,
    INSTR_GTRI,
    INSTR_GTRR,
    INSTR_EQIR,
    INSTR_EQRI,
    INSTR_EQRR,
    INSTR_ID_COUNT
};

struct instr {
    enum instr_id i;
    int a;
    int b;
    int c;
};

struct sample {
    reg_t before[REGS];
    reg_t after[REGS];
    struct instr instr;
};

const char *instr_str[] = {
    "addr",
    "addi",
    "mulr",
    "muli",
    "banr",
    "bani",
    "borr",
    "bori",
    "setr",
    "seti",
    "gtir",
    "gtri",
    "gtrr",
    "eqir",
    "eqri",
    "eqrr"
};

void instr_interpret(reg_t *r, struct instr *i)
{
    switch (i->i) {
    case INSTR_ADDR:
    case INSTR_MULR:
    case INSTR_BANR:
    case INSTR_BORR:
    case INSTR_GTRR:
    case INSTR_EQRR:
        if (i->b >= REGS) return;
        // fallthrough
    case INSTR_ADDI:
    case INSTR_MULI:
    case INSTR_BANI:
    case INSTR_BORI:
    case INSTR_SETR:
    case INSTR_GTRI:
    case INSTR_EQRI:
        if (i->a >= REGS) return;
        // fallthrough
    case INSTR_SETI:
        if (i->c >= REGS) return;
        break;

    case INSTR_GTIR:
    case INSTR_EQIR:
        if (i->b >= REGS) return;
        if (i->c >= REGS) return;
        break;

    default:
        break;
    }

    switch (i->i) {
    case INSTR_ADDR: r[i->c] = r[i->a] + r[i->b]; break;
    case INSTR_ADDI: r[i->c] = r[i->a] + i->b; break;
    case INSTR_MULR: r[i->c] = r[i->a] * r[i->b]; break;
    case INSTR_MULI: r[i->c] = r[i->a] * i->b; break;
    case INSTR_BANR: r[i->c] = r[i->a] & r[i->b]; break;
    case INSTR_BANI: r[i->c] = r[i->a] & i->b; break;
    case INSTR_BORR: r[i->c] = r[i->a] | r[i->b]; break;
    case INSTR_BORI: r[i->c] = r[i->a] | i->b; break;
    case INSTR_SETR: r[i->c] = r[i->a]; break;
    case INSTR_SETI: r[i->c] = i->a; break;
    case INSTR_GTIR: r[i->c] = (i->a > r[i->b]) ? 1 : 0; break;
    case INSTR_GTRI: r[i->c] = (r[i->a] > i->b) ? 1 : 0; break;
    case INSTR_GTRR: r[i->c] = (r[i->a] > r[i->b]) ? 1 : 0; break;
    case INSTR_EQIR: r[i->c] = (i->a == r[i->b]) ? 1 : 0; break;
    case INSTR_EQRI: r[i->c] = (r[i->a] == i->b) ? 1 : 0; break;
    case INSTR_EQRR: r[i->c] = (r[i->a] == r[i->b]) ? 1 : 0; break;
    default: break;
    }
}

struct sample *parse_samples(const char *fname, int *len,
                             struct instr **program, int *program_len)
{
    FILE *f = fopen(fname, "r");
    if (!f) {
        perror(fname);
        return NULL;
    }

    GArray *array = g_array_new(FALSE, FALSE, sizeof(struct sample));

    // Haha what is proper parsing
    struct sample sample;
    while (fscanf(f,
            "Before: [%ld, %ld, %ld, %ld]\n"
            "%d %d %d %d\n"
            "After:  [%ld, %ld, %ld, %ld]\n\n",
            &sample.before[0], &sample.before[1],
            &sample.before[2], &sample.before[3],
            (int *)&sample.instr.i, &sample.instr.a,
            &sample.instr.b, &sample.instr.c,
            &sample.after[0], &sample.after[1],
            &sample.after[2], &sample.after[3]
            ) == 12) {
        g_array_append_val(array, sample);
    }

    fscanf(f, "\n\n");

    GArray *prog_array = g_array_new(FALSE, FALSE, sizeof(struct instr));

    struct instr instr;
    while (fscanf(f, "%d %d %d %d\n",
            (int *)&instr.i, &instr.a, &instr.b, &instr.c) == 4) {
        g_array_append_val(prog_array, instr);
    }

    fclose(f);

    *program_len = prog_array->len;
    *program = (struct instr *)g_array_free(prog_array, FALSE);

    *len = array->len;
    return (struct sample *)g_array_free(array, FALSE);
}

int main()
{
    int samples_len;
    struct instr *program;
    int program_len;
    struct sample *samples = parse_samples("input", &samples_len,
                                           &program, &program_len);
    if (!samples) return 1;

    reg_t *regs = g_new0(reg_t, REGS);
    enum instr_id *mapping = g_new(enum instr_id, INSTR_ID_COUNT);

    for (enum instr_id *map = mapping;
            map < mapping + INSTR_ID_COUNT; map++) {
        *map = INSTR_ID_COUNT;
    }

    int changed = 1;

    while (changed) {
        changed = 0;

        for (enum instr_id id = 0; id < INSTR_ID_COUNT; id++) {
            if (mapping[id] != INSTR_ID_COUNT) continue;

            int possible[INSTR_ID_COUNT] = {[0 ... INSTR_ID_COUNT - 1] = 1};
            for (enum instr_id *map = mapping;
                    map < mapping + INSTR_ID_COUNT; map++) {
                if (*map != INSTR_ID_COUNT) possible[*map] = 0;
            }

            for (struct sample *sample = samples;
                    sample < samples + samples_len; sample++) {
                if (sample->instr.i != id) continue;

                struct instr instr;
                memcpy(&instr, &sample->instr, sizeof(struct instr));
                for (enum instr_id i = 0; i < INSTR_ID_COUNT; i++) {
                    if (!possible[i]) continue;

                    instr.i = i;
                    memcpy(regs, sample->before, sizeof(reg_t) * REGS);
                    instr_interpret(regs, &instr);
                    if (memcmp(regs, sample->after, sizeof(reg_t) * REGS) != 0) {
                        possible[i] = 0;
                    }
                }
            }

            printf("%02d: ", id);
            for (enum instr_id i = 0; i < INSTR_ID_COUNT; i++) {
                if (possible[i]) printf("%s ", instr_str[i]);
            }
            putchar('\n');

            int tally = 0;
            for (int *i = possible; i < possible + INSTR_ID_COUNT; i++) tally += *i;
            if (!tally) {
                fprintf(stderr, "Instruction %d could not be identified!\n", id);
                goto error;
            }
            if (tally != 1) continue;

            for (enum instr_id i = 0; i < INSTR_ID_COUNT; i++) {
                if (possible[i]) {
                    mapping[id] = i;
                    break;
                }
            }
            changed = 1;
            printf("-- %02d: %s (%02d)\n", id, instr_str[mapping[id]], mapping[id]);
        }
    }

    putchar('\n');
    for (int i = 0; i < INSTR_ID_COUNT; i++) {
        printf("%02d: %s (%02d)\n", i, instr_str[mapping[i]], mapping[i]);
    }

    memset(regs, 0, sizeof(reg_t) * REGS);
    for (struct instr *instr = program;
            instr < program + program_len; instr++) {
        if (instr->i >= INSTR_ID_COUNT) {
            fprintf(stderr, "ERROR: Invalid instruction ID %d\n", (int)instr->i);
            goto error;
        }

        instr->i = mapping[instr->i];
        instr_interpret(regs, instr);
    }

    printf("%lu\n", regs[0]);

error:
    g_free(mapping);
    g_free(regs);
    g_free(program);
    g_free(samples);
    return 0;
}