/* rpick.c -- generate a random pick
 * 
 * int	n, N;
 * int	pick[n];
 * rpick(n, N, pick);
 *
 * rpick pick n elements at random from N.  The n elements chosen are
 * returned in pick.  They will be distinct and ordered from small to
 * large.  The pick[i] range from 0 to N-1.
 */
#include <stdio.h>
#include "common.h"

int	irand();

void
rpick(n, N, pick)
int		n, N;
int		pick[];
{
    register int	i, j, k;
    int			p;

    if (				/* make sure values valid	*/
	(n < 0) ||
	(N < 0) ||
	(N < n)
    ) return;
    for(i=0; i<n; i++) {
	p = irand(N-i);
	for(k=0; k<i; k++) {
	    if (pick[k] > p) break;
	    p++;
	}
	for(j=i; j>k; j--) {
	    pick[j] = pick[j-1];
	}
	pick[k] = p;
    }
}