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).
这个题，如果不知道3sum双指针的做法，做起来会比较麻烦。
class Solution { public: int threeSumClosest(vector<int> &num, int target) { sort(num.begin(),num.end()); int min = -1; int re = 0; for(int i = 0 ; i < num.size()-2;i++) { int tar =target - num[i]; int left = i+1,right = num.size()-1; while(left < right) { int now = abs(tar - num[left] -num[right]); if(min<0) { min = now; re = num[i] + num[left] + num[right]; } if(now < min) {min = now;re = num[i] + num[left] + num[right];} if(tar > num[left] + num[right]) left++; else if((tar < num[left] + num[right])) right --; else return target; } } return re; } };
原文：http://www.cnblogs.com/pengyu2003/p/3585978.html