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/*
* Copyright (C) 2012-2015 Olivier Gayot
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <stdint.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <stdbool.h>
typedef uint8_t byte;
typedef int8_t rang_t;
typedef struct {
byte value;
rang_t rang;
} elem_t;
typedef struct {
int len;
elem_t *elem;
} map_t;
map_t *map_g;
/* resolve {{{ */
/* returns true if the map is empty, otherwise returns false */
static bool map_is_empty(void)
{
for (int i = 0; i < map_g->len; i++) {
if (map_g->elem[i].rang == -1) {
return false;
}
}
return true;
}
/* return the index of the next element */
static inline int get_next_case(int current)
{
return (current + map_g->elem[current].value) % map_g->len;
}
/* return the index of the previous element */
static inline int get_prev_case(int current)
{
int prev = current - map_g->elem[current].value;
if (current < map_g->elem[current].value)
prev += map_g->len;
return prev;
}
static int perform_resolve_god_hands(int activated, int offset)
{
int next, prev;
/* this one is already activated, not possible captain */
if (map_g->elem[activated].rang != -1) {
return -1;
}
/* activate the current case */
map_g->elem[activated].rang = offset;
if (map_is_empty()) {
/* we won */
return 0;
}
next = get_next_case(activated);
prev = get_prev_case(activated);
if (perform_resolve_god_hands(next, offset + 1) == 0)
return 0;
if (perform_resolve_god_hands(prev, offset + 1) == 0)
return 0;
/* reset to default */
map_g->elem[activated].rang = -1;
return -1;
}
int solve_god_hands(map_t *map)
{
for (int i = 0; i < map->len; i++) {
map->elem[i].rang = -1;
}
map_g = map;
for (int i = 0; i < map->len; i++) {
if (perform_resolve_god_hands(i, 0) == 0) {
return 0;
}
}
return -1;
}
/* }}} */
static void display_solution(const map_t *map)
{
for (int i = 0; i < map->len; i++) {
/* run through the order */
for (int j = 0; j < map->len; j++) {
/* run through the elems */
assert (map->elem[j].rang != -1);
if (map->elem[j].rang == i) {
printf("[%d] ", j);
break;
}
}
}
putchar('\n');
}
int main(void)
{
map_t map;
char buffer[16];
/* get the length of the map */
for (;;) {
if (isatty(STDIN_FILENO) && isatty(STDOUT_FILENO)) {
fputs("size of the map: ", stdout);
}
if (fgets(buffer, sizeof(buffer), stdin) == NULL) {
return 0;
}
/* TODO replace with strtol to handle errors of type 42(.*) */
map.len = atoi(buffer);
if (map.len <= 0) {
fprintf(stderr, "the map has an invalid size\n");
if (!isatty(STDIN_FILENO))
return -1;
continue;
}
break;
}
map.elem = malloc(sizeof(elem_t) * map.len);
for (int i = 0; i < map.len; i++) {
if (isatty(STDIN_FILENO) && isatty(STDOUT_FILENO))
printf("(%02d/%02d): ", i + 1, map.len);
fflush(stdout);
if (fgets(buffer, sizeof(buffer), stdin) == NULL) {
return 0;
}
/* TODO check for errors (i.e. not numbers and negative values */
map.elem[i].value = atoi(buffer);
}
if ((solve_god_hands(&map)) != 0) {
fputs("cannot solve the paradox, kupo :-/\n", stderr);
} else {
fputs("we solved the paradox kupo! :-)\n", stdout);
display_solution(&map);
}
return 0;
}
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