Sum2Plus2.java

import java.util.ArrayList;
import java.util.HashMap;


public class Sum2Plus2 {
	public static int[] Sum4DifferenceIndex(int[] a) {
		HashMap<Integer, ArrayList<Integer>> map = new HashMap<Integer, ArrayList<Integer>>();
		for(int i = 0; i < a.length;i++) {
			for(int j=i+1; j< a.length; j++) {
				int sum = a[i]+a[j];
				if(map.containsKey(sum)) {
					int p = map.get(sum).get(0);
					int q = map.get(sum).get(1);
					if(i!=q && j!=p) {
						//System.out.print(true);
						return new int[]{i,j,p,q};
					}
				}
				else {
					ArrayList<Integer> list = new ArrayList<Integer>();
					list.add(i);
					list.add(j);
					map.put(sum, list);
				}
			}
		}
		//System.out.print(false);
		return new int[] {-1};
	}

	public static void main(String[] args) {
		int[] a = new int[] {1,11,4,2,3};
		int[] result = Sum4DifferenceIndex(a);
		for(int index: result) {
			System.out.print(index+ " ");
		}
		
		
	}
}