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).

其实经过3sum，这一题应该还挺简单的！设置一个gap,根据gap的状态来移动指针

class Solution {public:int threeSumClosest(vector<int> &num,int target) {int result=INT_MAX;int temp = 0;int gap = INT_MAX;if (num.size()<3)return INT_MAX;sort(num.begin(),num.end());typedef vector<int>::iterator it;it mid;it last;result = INT_MAX;for (it start = num.begin(); start != num.end() - 1;++start){if (start != num.begin()){if (*start == *(start - 1))continue;}mid = start + 1;last =  num.end() - 1;while (mid<last){temp = abs((*start + *mid + *last - target));if (gap > temp ){result = *start + *mid + *last;gap = temp;}if ((*start + *mid + *last - target) < 0){++mid;}else--last;}}return result;}};