182 lines
4.0 KiB
C
182 lines
4.0 KiB
C
/* aoc-c: Advent2021 game, 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.htmlL>.
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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 <malloc.h>
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#include "debug.h"
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#include "bits.h"
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static int ex1()
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{
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u32 length, gamma = 0, epsilon = 0;
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char buffer[80];
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s32 *values;
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/* get length of binary number */
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scanf("%s", buffer);
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length = strlen(buffer);
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values = calloc(length, sizeof(*values));
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do {
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for (u32 i = 0; i < length; ++i) {
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switch (buffer[i]) {
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case '0':
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values[i]--;
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break;
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case '1':
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values[i]++;
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break;
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}
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}
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} while (scanf("%s", buffer) != EOF);
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for (u32 i = 0; i < length; ++i) {
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if (values[i] > 0)
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gamma += 1 << (length-i-1);
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else
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epsilon += 1 << (length-i-1);
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}
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free (values);
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return gamma * epsilon;
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}
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static int ex2()
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{
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u32 length, size, *values, min, max, oxygen, co2;
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u32 zero, one, lastone, lastzero, bit;
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char buffer[80];
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u64 val;
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/* get length of binary number */
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scanf("%s", buffer);
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length = strlen(buffer);
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size = 1 << length;
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values = calloc(size, sizeof(*values));
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do {
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val = strtoul(buffer, NULL, 2);
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values[val] = val;
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} while (scanf("%s", buffer) != EOF);
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min = 0;
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max = size;
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bit = size >> 1;
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while (1) {
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zero = 0;
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one = 0;
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for (u32 i = min; i < max; ++i) {
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if (values[i]) {
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if (values[i] & bit) {
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one++;
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lastone = i;
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} else {
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zero++;
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lastzero = i;
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}
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}
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}
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if (one >= zero) {
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if (one == 1) {
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oxygen = lastone;
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break;
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}
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min = (max + min) / 2;
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} else {
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if (zero == 1) {
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oxygen = lastzero;
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break;
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}
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max = (max + min) / 2;
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}
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bit >>= 1;
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}
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min = 0;
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max = size;
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bit = size >> 1;
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while (1) {
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zero = 0;
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one = 0;
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for (u32 i = min; i < max; ++i) {
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if (values[i]) {
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if (values[i] & bit) {
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one++;
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lastone = i;
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} else {
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zero++;
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lastzero = i;
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}
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}
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}
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if (zero <= one) {
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if (zero == 1) {
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co2 = lastzero;
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break;
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}
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max = (max + min) / 2;
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} else {
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if (one == 1) {
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co2 = lastone;
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break;
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}
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min = (max + min) / 2;
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}
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bit >>= 1;
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}
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free(values);
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return oxygen * co2;
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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;
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u32 exercise = 1, res;
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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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exercise = atoi(optarg);
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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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if (exercise == 1) {
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res = ex1();
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printf ("%s : res=%d\n", *av, res);
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} else {
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res = ex2();
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printf ("%s : res=%d\n", *av, res);
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}
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exit (0);
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}
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