[leetcode]16. 3Sum Closest

题目链接：https://leetcode.com/problems/3sum-closest/#/description

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).

class Solution{public:    int threeSumClosest(vector<int>& nums,int target)    {        sort(nums.begin(),nums.end());        if(nums.size()<3)            return 0;        int res=nums[0]+nums[1]+nums[2];        for(int i=0;i<nums.size()-2;i++)        {            int j=i+1,k=nums.size()-1;            while(j<k)            {                int num=nums[i]+nums[j]+nums[k];                if(abs(num-target)<abs(res-target)) res=num;                if(num>target) k--;                else j++;            }        }        return res;    }};