[leetcode]16. 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).

先看别人的解法写的15题，再写16题觉得还是比较easy的

最开始没有加if(sum==target)  return target，对有些测试集显示超时，其实只要找到了sum==target就不需要再继续判断了

class Solution {public:    int threeSumClosest(vector<int>& nums, int target) {        int length = nums.size();   //     sort(nums.begin(),nums.end());        int closest = 2147483647;        for(int i=0; i<length; i++)        {            for(int j=i+1; j<length; j++)            {                for(int k=j+1; k<length; k++)                {                    int sum = nums[i] + nums[j] + nums[k];                    if(sum==target)                        return target;                    if(abs(sum-target)<abs(closest))                        closest = sum- target;                }            }        }        return (target+closest);    }};