151 lines
3.6 KiB
C
151 lines
3.6 KiB
C
/* aoc-c.c: Advent of Code 2019, day 2 parts 1 & 2
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*
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* Copyright (C) 2021 Bruno Raoult ("br")
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* Licensed under the GNU General Public License v3.0 or later.
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* Some rights reserved. See COPYING.
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*
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* You should have received a copy of the GNU General Public License along with this
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* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
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*
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* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include "debug.h"
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typedef enum {
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ADD = 1,
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MUL = 2,
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RET = 99
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} opcode_t;
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#define MAXOPS 1024
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struct program {
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int length; /* total program length */
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int cur; /* current position */
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int ops[MAXOPS]; /* should really be dynamic */
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};
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#define OP(p) ((p)->ops + (p)->cur)
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#define A1(p) ((p)->ops + *((p)->ops + (p)->cur + 1))
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#define A2(p) ((p)->ops + *((p)->ops + (p)->cur + 2))
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#define A3(p) ((p)->ops + *((p)->ops + (p)->cur + 3))
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static int run(struct program *prog)
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{
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while (1) {
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opcode_t opcode = *OP(prog);
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switch (opcode) {
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case ADD:
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*A3(prog) = *A1(prog) + *A2(prog);
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break;
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case MUL:
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*A3(prog) = *A1(prog) * *A2(prog);
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break;
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case RET:
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return prog->ops[0];
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default:
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fprintf(stderr, "wrong opcode %d at %d.\n", opcode, prog->cur);
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exit (1);
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}
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prog->cur += 4;
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}
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return -1;
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}
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static struct program *parse()
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{
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size_t alloc = 0;
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ssize_t buflen;
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char *buf = NULL, *token;
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int input;
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struct program *prog = NULL;
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if ((buflen = getline(&buf, &alloc, stdin)) <= 0) {
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fprintf(stderr, "error reading file.\n");
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goto end;
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}
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if (!(prog = calloc(1, sizeof(struct program)))) {
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fprintf(stderr, "cannot allocate program.\n");
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goto freebuf;
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}
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for (token = strtok(buf, ","); token; token = strtok(NULL, ",")) {
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if (prog->length >= MAXOPS - 1) {
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fprintf(stderr, "overflow !\n");
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free(prog);
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prog = NULL;
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goto freebuf;
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}
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input=atoi(token);
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prog->ops[prog->length++] = input;
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}
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freebuf:
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free(buf);
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end:
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return prog;
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}
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static int part1(struct program *p)
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{
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p->ops[1] = 12;
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p->ops[2] = 2;
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return run(p);
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}
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static int part2(struct program *p)
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{
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struct program work;
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for (int noun = 0; noun < 100; ++noun) {
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for (int verb = 0; verb < 100; ++verb) {
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work = *p;
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work.ops[1] = noun;
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work.ops[2] = verb;
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if (run(&work) == 19690720)
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return noun * 100 + verb;
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}
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}
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return -1;
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}
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static int usage(char *prg)
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{
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fprintf(stderr, "Usage: %s [-d debug_level] [-p part]\n", prg);
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return 1;
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}
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int main(int ac, char **av)
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{
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int opt, part = 1;
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struct program *p;
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while ((opt = getopt(ac, av, "d:p:")) != -1) {
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switch (opt) {
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case 'd':
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debug_level_set(atoi(optarg));
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break;
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case 'p': /* 1 or 2 */
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part = atoi(optarg);
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if (part < 1 || part > 2)
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return usage(*av);
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break;
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default:
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return usage(*av);
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}
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}
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if (optind < ac)
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return usage(*av);
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p = parse();
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printf("%s : res=%d\n", *av, part == 1? part1(p): part2(p));
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free(p);
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exit (0);
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}
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