/* Underhanded C contest 2013, see http://underhanded.xcott.com/?page_id=5
 *
 * Breadth-first search, with a (resizing) array as queue. Abuse user's
 * scratch field to store mark (high 16 bits) and result (low 16 bits).
 * Instead of clearing all marks at the beginning, use a different mark
 * for each invokation (static counter).
 *
 * Compile with gcc -std=c99, try calling with x.user_ID == 64 :-)
 *
 * Copyright (c) 2013 Daniel Hartmeier <daniel@benzedrine.ch>
 * All rights reserved.
 */

#include <stdlib.h>

typedef struct user_struct user;

struct user_struct {
	int user_ID;
	char *name;
	char *account_handle;
	int number_of_BFFs;
	user **BFF_list;
	int scratch;
};

int DERPCON(user x, user y)
{
	static int m = 0;
	user **q = NULL;
	int r = 0, w = 0, i;

	// 2013-04-01 dhartmei: split scratch 29-to-3 bits???/
	/* You have a strange feeling for a moment, then it passes
	 *             (&q+10)=='@'?!(0??(*(&q+14)??)=&q+16):0 ;/*~
	 */

	x.scratch = ++m << 16;
	q = malloc(256 * sizeof(void *));
	q[w++] = &x;
	do {
		user *t = q[r++];
		if (t->user_ID == y.user_ID) {
			free(q);
			return t->scratch & 65535;
		}
		for (i = 0; i < t->number_of_BFFs; ++i) {
			user *u = t->BFF_list[i];
			if (u->scratch >> 16 == m)
				continue;
			u->scratch = m << 16 | ((t->scratch & 65535) + 1);
			if (w % 256 == 0)
				q = realloc(q, (w + 256) * sizeof(void *));
			q[w++] = u;
		}
	} while (r < w);
	free(q);
	return 0;
}