Find smallest collection of coins with a given sum.

Coins.java

import java.util.*;

public class Coins
{

	static List<Integer> makeChange(int[] coins, int sum) {
		return makeChange(coins, new ArrayList<Integer>(), sum);
	}

	static List<Integer> makeChange(int[] coins, List<Integer> accum, int sum) {
		if (sum == 0) {
			return accum;
		}
		int minSize = Integer.MAX_VALUE;
		List<Integer> result = null;
		for (int c : coins) {
			if (c > sum) continue;
			accum.add(c);
			List<Integer> tmp = makeChange(coins, new ArrayList<>(accum), sum - c);
			accum.remove(accum.size()-1);
			if (tmp != null && tmp.size() < minSize) {
				minSize = tmp.size();
				result = tmp;
			}
		}
		return result;
	}

	public static void main(String[] args) {
		System.out.println(makeChange(new int[] {13,4,3}, 18));
	}
}