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.

思路：同３Ｓｕｍ题目，使用三个指针。

    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).

#include <stdlib.h>#include <algorithm>class Solution {public:    int threeSumClosest(vector<int>& nums, int target) {        if(nums.size() < 3)            return 0;        int result = nums[0] + nums[1] + nums[2];        sort(nums.begin(), nums.end());        for(int i = 0 ; i <= nums.size()-3; i++)        {            int j = i + 1;            int k = nums.size() - 1;            while(j < k){                int sum = nums[i] + nums[j] + nums[k];                if(sum > target){                    k--;                }                else if(sum < target){                    j++;                }else                    return target;                //update the sum.                if(abs(sum - target) < abs(result - target)){                    result = sum;                }            }        }        return result;    }};