Array shuffle and unshuffle

#include <stdio.h>

#define printd(A) printf(#A" = %d\n", A)

int * shuffle(int * array, int seed, int index, int len);
int * unshuffle(int * array, int seed, int index, int len);
void swap(int * num1, int * num2);
void printArray(int * array, int len);

int main()
{
    int vec[5] = {1, 2, 3, 4, 5};
    shuffle(vec, 1, 0, 5);
    printArray(vec, 5);
    puts("\n");
    unshuffle(vec, 1, 0, 5);
    printArray(vec, 5);
    return 0;
}

int * shuffle(int * array, int seed, int index, int len)
{
    int result;
    if(index == len)
        return array;
    srand(seed);
    result = rand();
    swap(&array[index], &array[result%len]);
    return shuffle(array, result, index + 1, len);
}

int * unshuffle(int * array, int seed, int index, int len)
{
    int result;
    if(index == len)
        return array;
    srand(seed);
    result = rand();
    array = unshuffle(array, result, index + 1, len);
    swap(&array[index], &array[result%len]);
    return array;
}

void swap(int * num1, int * num2)
{
    int temp = *num1;
    *num1 = *num2;
    *num2 = temp;
}

void printArray(int * array, int len)
{
    int i;
    for(i = 0; i < len; i++)
        printf("array[%d] = %d\n", i, array[i]);
}