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A Java API for Meta-CSP based reasoning

There is a newer version: 1.3.5

package org.metacsp.utility;
// Combinations.java
// Computes nCr -- all the ways you can combine r choices among n total objects.
// Unlike permutations, here order does not matter, so {0,1,2} is the same as {0,2,1}.

import java.util.*;







//////////////////////////////////////
// Combination
//
// You do not need to write the code below here.
// You just need to be able to USE it.
//////////////////////////////////////

// The algorithm is from Applied Combinatorics, by Alan Tucker.
// Based on code from koders.com

public class Combination {
	private int n, r;
	private int[] index;
	private boolean hasNext = true;

	public Combination(int n, int r) {
		this.n = n;
		this.r = r;
		index = new int[r];
		for (int i = 0; i= 0) {
			index[i] = index[i]+1; 
			for (int j = i+1; j=0; i--)
			if (index[i] < n - r + i) return i;
		return -1;
	}

	public static void main(String[] args) {
		Combination c = new Combination(4,2);

		while (c.hasNext()) {
			int[] a = c.next();
			System.out.println(Arrays.toString(a));
		}
	}

}