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) return 0;

 4         int min = Integer.MAX_VALUE, len = num.length;

 5         Arrays.sort(num);

 6         for(int i = 0; i < len - 2; i ++){

 7             int goal = target - num[i];

 8             int j = i + 1, k = len - 1;

 9             while(j < k){

10                 min = Math.abs(min) < Math.abs(target - num[i] - num[j] - num[k]) ? min : (target - num[i] - num[j] - num[k]);

11                 if(num[j] + num[k] < goal) j ++;

12                 else if(num[j] + num[k] > goal) k --;

13                 else return target;

14             }

15         }

16         return target - min;

17     }

18 }