Leetcode: 3Sum Closest

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

    For example, given array S = {-1 2 1 -4}, and target = 1.

    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

 1 public class Solution {
 2     public int threeSumClosest(int[] num, int target) {
 3         if (num==null || num.length<3) {
 4             return Integer.MIN_VALUE;
 5         }
 6         int res = num[0] + num[1] + num[2] - target;
 7         Arrays.sort(num);
 8         for (int i=num.length-1; i>=2; i--) {
 9             int cur = twoSum(num, target-num[i], 0, i-1);
10             if (Math.abs(cur) < Math.abs(res)) {
11                 res = cur;
12             }
13         }
14         return target+res;
15     }
16     
17     public int twoSum(int[] num, int target, int l, int r) {
18         int closest = num[l] + num[r] - target;
19         while (l < r) {
20             if (num[l] + num[r] == target) {
21                 return 0;
22             }
23             int diff = num[l] + num[r] - target;
24             if (Math.abs(diff) < Math.abs(closest)) {
25                 closest = diff;
26             }
27             if (num[l] + num[r] > target) {
28                 r--;
29             }
30             else {
31                 l++;
32             }
33         }
34         return closest;
35     }
36 }