permut.c

#include "permut-1.0.h"
#include "fact.h"

void swap(int *sequence, int i, int j) {
	int tmp;
	tmp = sequence[i];
	sequence[i] = sequence[j];
	sequence[j] = tmp;
}

void permut(int *sequence, size_t size, unsigned int index) {
	int pos;
	int factorial = fact(--size);
	do {
		pos = index / factorial;

		index %= factorial;
		factorial /= size;
		swap(sequence, pos, size);
	} while (--size);
}