Fisher-Yates array shuffle

shuffle.c

#include <stdio.h>
#include <stdlib.h>

#define N 10

static int A[N];

static unsigned int seed;

static void swap(int *a, int *b)
{
    int tmp = *a;
    *a = *b;
    *b = tmp;
}

// Fisher-Yates shuffle
static void shuffle(int *A, int len)
{
    int rand, i;
    for (i = len-1; i > 0; i--) {
        rand = rand_r(&seed) % (i + 1);
        swap(&A[rand], &A[i]);
    }
}

int main(void)
{
	int i;

	for (i = 0; i < N; i++) {
		A[i] = i;
		printf("A[%d] = %d\n", i, A[i]);
	}

	printf("\n");

	seed = 100;
	shuffle(A, N);

	for (i = 0; i < N; i++) {
		printf("A[%d] = %d\n", i, A[i]);
	}

	printf("\n");
	
	shuffle(A, N);

	for (i = 0; i < N; i++) {
		printf("A[%d] = %d\n", i, A[i]);
	}

	return 0;
}