day 9 (C)
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236
2021/day09/aoc-c.c
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236
2021/day09/aoc-c.c
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/* aoc-c: Advent2021 game, day 6 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 <malloc.h>
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#include "debug.h"
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#include "bits.h"
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#include "list.h"
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#include "pool.h"
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#define NLINES 1024 /* alloc size */
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struct data {
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int nlines; /* current read lines */
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int alloc; /* allocated lines */
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int length; /* line length */
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char **lines;
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};
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#ifdef DEBUG
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static void print_data(struct data *data)
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{
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for (int i = 0; i < data->nlines; ++i)
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printf("[%03d]%s\n", i, data->lines[i]);
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}
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#endif
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static struct data *read_file()
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{
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size_t alloc = 0;
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static struct data data;
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ssize_t len;
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data.alloc = NLINES;
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if (!(data.lines = malloc(data.alloc * sizeof (*data.lines))))
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return NULL;
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while ((len = getline(&data.lines[data.nlines], &alloc, stdin)) > 0) {
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data.length = len - 1;
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data.lines[data.nlines][len - 1] = 0;
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if (data.nlines == data.alloc) {
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data.alloc += NLINES;
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if (!(data.lines = realloc(data.lines, data.alloc * sizeof (*data.lines))))
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return NULL;
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}
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data.nlines++;
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}
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return &data;
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}
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#define UP(l, c) (data->lines[(l) - 1][c])
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#define DOWN(l, c) (data->lines[(l) + 1][c])
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#define LEFT(l, c) (data->lines[l][(c) - 1])
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#define RIGHT(l, c) (data->lines[l][(c) + 1])
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static u64 part1()
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{
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int res = 0;
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struct data *data;
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int l, c;
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data = read_file();
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for (l = 0; l < data->nlines; ++l) {
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for (c = 0; c < data->length; ++c) {
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if (l > 0) {
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if (UP(l, c) <= data->lines[l][c])
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continue;
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}
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if (c > 0) {
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if (LEFT(l, c) <= data->lines[l][c])
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continue;
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}
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if (l < data->nlines - 1) {
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if (DOWN(l, c) <= data->lines[l][c])
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continue;
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}
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if (c < data->length - 1) {
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if (RIGHT(l, c) <= data->lines[l][c])
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continue;
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}
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res += data->lines[l][c] - '0' + 1;
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}
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}
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return res;
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}
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struct stack {
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int l;
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int c;
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struct list_head list;
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};
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LIST_HEAD(stack_head);
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static pool_t *pool;
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static struct stack *push(int l, int c)
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{
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struct stack *stack;
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stack = pool_get(pool);
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stack->l = l;
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stack->c = c;
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list_add_tail(&stack->list, &stack_head);
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return stack;
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}
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static struct stack *pop()
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{
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struct stack *stack;
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if (list_empty(&stack_head))
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return NULL;
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stack = list_first_entry(&stack_head, struct stack, list);
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list_del(&stack->list);
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return stack;
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}
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static int bfs(struct data *data)
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{
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struct stack *stack;
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int res = 0, l, c;
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while ((stack = pop())) {
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l = stack->l;
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c = stack->c;
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res++;
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pool_add(pool, stack);
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if (l > 0) {
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if (UP(l, c) < '9') {
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data->lines[l - 1][c] = '9';
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push(l - 1, c);
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}
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}
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if (c > 0) {
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if (LEFT(l, c) < '9') {
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data->lines[l][c - 1] = '9';
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push(l, c - 1);
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}
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}
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if (l < data->nlines - 1) {
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if (DOWN(l, c) < '9') {
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data->lines[l + 1][c] = '9';
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push(l + 1, c);
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}
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}
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if (c < data->length - 1) {
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if (RIGHT(l, c) < '9') {
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data->lines[l][c + 1] = '9';
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push(l, c + 1);
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}
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}
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}
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return res;
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}
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static u64 part2()
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{
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int res = 0, l, c, best[3] = { 0 }, lowbest;
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struct data *data;
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data = read_file();
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if (!(pool = pool_init("stack", 128, sizeof (struct stack))))
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return -1;
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for (l = 0; l < data->nlines; ++l) {
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for (c = 0; c < data->length; ++c) {
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if (data->lines[l][c] < '9') {
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data->lines[l][c] = '9';
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push(l, c);
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res = bfs(data);
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lowbest = 0;
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if (best[1] < best[lowbest])
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lowbest = 1;
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if (best[2] < best[lowbest])
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lowbest = 2;
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if (res > best[lowbest])
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best[lowbest] = res;
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}
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}
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}
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return best[0] * best[1] * best[2];
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}
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static u64 doit(int part)
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{
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return part == 1? part1(): part2();
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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;
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u64 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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if (exercise < 1 || exercise > 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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res = doit(exercise);
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printf("%s : res=%lu\n", *av, res);
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exit (0);
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}
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