LeetCode 3Sum Closest

题目：

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> &num, int target) {    int minVal = INT_MAX;    int len = num.size();    sort(num.begin(), num.end());    int ans, sum;    for(int i = 0; i < len-2; i++) {    int begin = i+1, end = len-1;    while(begin < end) {    sum = num[i] + num[begin] + num[end];    if(abs(sum-target) < minVal) {    minVal = abs(sum-target);    ans = sum;    }    if(sum == target)    return ans;    else if(sum < target)    begin++;    else    end--;        }     }    return ans;       }};