Given a hand of n cards and k attempts, use recursion to shuffle the cards into a given order.

reorderhand.c

/**
 * Emil Hernvall - 2007-12-15
 * Given a hand of n cards and k attempts, use recursion to shuffle the cards
 * into a given order.
 */

#include <stdio.h>

int compare(int* first, int* second, int size)
{
	int i;
	for (i = 0; i < size; i++) {
		if (first[i] != second[i]) {
			return 0;
		}
	}

	return 1;
}

void print(int* source, int size, int indent)
{
	int i;
	for (i = 0; i < indent; i++) {
		printf("\t");
	}
	for (i = 0; i < size; i++) {
		printf("%d ", source[i]);
	}
	printf("\n");
}

int* move(int* source, int size, int pos, int range, int newpos)
{
	int* new = malloc(sizeof(int) * size);
	memset(new, 0, sizeof(int) * size);

	int move[range];
	int fixed[size-range];
	
	// separate the interval to move and the fixed cards
	int i, j, k;
	for (i = 0, j = 0, k = 0; i < size; i++) {
		if (i >= pos && i < pos + range) {
			move[j] = source[i];
			j++;
		} else {
			fixed[k] = source[i];
			k++;
		}
	}

	// merge them again
	for (i = 0, j = 0, k = 0; i < size; i++) {
		if (i >= newpos && i < newpos + range) {
			new[i] = move[j];
			j++;
		} else {
			new[i] = fixed[k];
			k++;
		}
	}

	return new;
}

int recurse(int* cards, int* target, int size, int maxlevel, int curlevel)
{
	if (curlevel > maxlevel) {
		return 0;
	}

	int i, j, n, match = 0;
	// number of cards to move every time
	for (n = 1; n < size; n++) {
		// position to move the cards from
		for (i = 0; i <= size - n; i++) {
			// position to move the cards to
			for (j = 0; j <= size - n; j++) {
				int* cards2 = move(cards, size, i, n, j);
				if (compare(cards2, target, size) == 1) {
					match = 1;
					print(cards2, size, curlevel);
				}
				else if (recurse(cards2, target, size, maxlevel, curlevel + 1) == 1) {
					match = 1;
					print(cards2, size, curlevel);
				}
				free(cards2);
			}
		}
	}

	return match;
}

int main(void)
{
	int size = 5;
	int cards[] = { 1, 2, 3, 4, 5 };
	int target[] = { 5, 4, 3, 2, 1 };

	recurse(cards, target, size, 3, 1);

	print(cards, size, 0);

	return 0;
}