127 lines
3.1 KiB
C
127 lines
3.1 KiB
C
/* aoc-c.c: Advent of Code 2019, day 4 parts 1 & 2
|
|
*
|
|
* Copyright (C) 2021 Bruno Raoult ("br")
|
|
* Licensed under the GNU General Public License v3.0 or later.
|
|
* Some rights reserved. See COPYING.
|
|
*
|
|
* You should have received a copy of the GNU General Public License along with this
|
|
* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
|
|
*
|
|
* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <malloc.h>
|
|
#include <errno.h>
|
|
#include <string.h>
|
|
#include <getopt.h>
|
|
|
|
#include "debug.h"
|
|
#include "likely.h"
|
|
|
|
/**
|
|
* next_number() - finds next suitable number after a faulty right digit
|
|
* @number: the number
|
|
* @faulty: the faulty digit position (1, 10, 100, etc...)
|
|
* @left: the left digit of faulty one
|
|
*
|
|
* This function is called when rule 4 is violated:
|
|
* "Going from left to right, the digits never decrease."
|
|
* Example: 453456
|
|
* ^
|
|
* Here we will replace the faulty digit and next ones with its left digit
|
|
* value (5 here). Returned number will be 455555.
|
|
* This function allowed to save 546,495/548,022 calls to is_valid(), which
|
|
* is 99.7%.
|
|
*/
|
|
static int next_number(int number, int faulty, int left)
|
|
{
|
|
int next = number - number % (faulty * 10);
|
|
|
|
for (; faulty; faulty /= 10)
|
|
next += left * faulty;
|
|
return next;
|
|
}
|
|
|
|
static int is_valid(int number, int part, int *next)
|
|
{
|
|
int valid = 0, dups[10] = { 0 }, work = number;
|
|
int digit, dec = number + 1, faulty = 1;
|
|
*next = number + 1;
|
|
|
|
for (digit = number % 10; number > 10; digit = dec, faulty *= 10) {
|
|
number /= 10;
|
|
dec = number % 10;
|
|
if (dec > digit) {
|
|
*next = next_number(work, faulty, dec);
|
|
return 0;
|
|
}
|
|
if (dec == digit) {
|
|
valid = 1;
|
|
dups[digit] += 2;
|
|
}
|
|
}
|
|
if (!valid || part == 1)
|
|
return valid;
|
|
for (int i = 0; i < 10; ++i)
|
|
if (dups[i] == 2)
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
static int doit(int *nums, int part)
|
|
{
|
|
int res = 0, next = 0;
|
|
|
|
for (int i = nums[0]; i < nums[1]; i = next) {
|
|
if (unlikely(is_valid(i, part, &next)))
|
|
res++;
|
|
}
|
|
return res;
|
|
}
|
|
|
|
static int *parse(int *res)
|
|
{
|
|
size_t alloc = 0;
|
|
char *buf = NULL;
|
|
|
|
getline(&buf, &alloc, stdin);
|
|
*res = atoi(strtok(buf, "-"));
|
|
*(res+1) = atoi(strtok(NULL, "-"));
|
|
free(buf);
|
|
return res;
|
|
}
|
|
|
|
static int usage(char *prg)
|
|
{
|
|
fprintf(stderr, "Usage: %s [-d debug_level] [-p part]\n", prg);
|
|
return 1;
|
|
}
|
|
|
|
int main(int ac, char **av)
|
|
{
|
|
int opt, part = 1;
|
|
int nums[2];
|
|
|
|
while ((opt = getopt(ac, av, "d:p:")) != -1) {
|
|
switch (opt) {
|
|
case 'd':
|
|
debug_level_set(atoi(optarg));
|
|
break;
|
|
case 'p': /* 1 or 2 */
|
|
part = atoi(optarg);
|
|
if (part < 1 || part > 2)
|
|
default:
|
|
return usage(*av);
|
|
}
|
|
}
|
|
if (optind < ac)
|
|
return usage(*av);
|
|
|
|
parse(nums);
|
|
printf("%s : res=%d\n", *av, doit(nums, part));
|
|
|
|
exit (0);
|
|
}
|