[LeetCode] 3Sum Closest

3Sum Closest

Given an arraySofnintegers, find three integers inSsuch 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).

解题思路：

类似于3Sum。首先给数组排序，，用两个变量分别记录当前最小距离和最近的和。代码如下，时间复杂度为O(n^2)

class Solution {public:int threeSumClosest(vector<int> &num, int target) {int len=num.size();if(len<3){return 0;}std::sort(num.begin(), num.end());int closest=num[0]+num[1]+num[2];int minDis = abs(closest-target);for(int i=0; i<len; i++){int start=i+1, end=len-1;while(start<end){int sum=num[i]+num[start]+num[end];int dis=abs(sum-target);if(dis<minDis){minDis=dis;closest=sum;}if(sum>target){end–;}else{start++;}}}return closest;}int abs(int a){return a>=0?a:-a;}};

我躺下来，以一张报纸当枕头。高高在我上方的，