4Sum

public class Solution {
    public ArrayList<ArrayList<Integer>> fourSum(int[] num, int target) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
    	Arrays.sort(num);
    	for (int i = 0; i < num.length; i++) {     		
                if (i > 0 && num[i] == num[i - 1])
    			continue;
    		for (int j = i + 1; j < num.length; j++) {     			
                        if (j > i + 1 && num[j] == num[j - 1] )
    				continue;
    			int p = j + 1, q = num.length - 1;
    			while (p < q) {
    				int sum = num[i] + num[j] + num[p] + num[q];
    				if (sum == target) {
    					ArrayList quad = new ArrayList();
    					quad.add(num[i]);
    					quad.add(num[j]);
    					quad.add(num[p]);
    					quad.add(num[q]);
					result.add(quad);
					do {p++;} while (p < q && num[p] == num[p - 1]);
					do {q--;} while (p < q && num[q] == num[q + 1]);
    				} else if (sum < target) {
    					p++;
    				} else {
    					q--;
    				}
    			}
    		}
    	}
    	return result;
    }
}