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). 这道题和上一道3sum很向，只要稍微改变一下就好了

1 public class Solution { 2     public int threeSumClosest(int[] num, int target) { 3         int result = Integer.MAX_VALUE;                    //最后返回的结果 4         int distance = Integer.MAX_VALUE; 5         Arrays.sort(num);                                 //对数组进行升序排序 6         boolean findTarget = false; 7          8         for(int i = 0; i < num.length; i++){ 9             int j = i + 1;10             int k = num.length - 1;                        //双指针11             while(j < k){12                 int sum = num[i] + num[k] + num[j];13                 if(target == sum){                        //等于target直接返回target的值14                     findTarget = true;15                     result = target;16                     break;17                 }18                 else if(sum > target){                    //sum比target大k前移,同时更新result,和距离19                     if(Math.abs(sum - target) < distance){20                         distance = Math.abs(sum - target);21                         result = sum;22                     }23                     k--;    24                 }25                 else{                                    //sum比target小，更新result和距离26                     if(Math.abs(sum - target) < distance){27                         distance = Math.abs(sum - target);28                         result = sum;29                     }30                     j++;31                 }32             }33             if(findTarget)34                 break;35         }36         37         return result;38     }39 }