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).

#include<iostream>
#include<vector>

using namespace std;
//穷举
int threeSumClosest(vector<int> &num, int target) {
	int ClosestTarget = INT_MAX;
	int ClosestLength = INT_MAX;
	for (int first = 0; first !=num.size();++first){
		for (int second = first + 1; second < num.size();++second){
			for (int third = second + 1; third < num.size();++third){
				int sum  = num[first] + num[second] + num[third];
				int temp = abs(sum-target);
				if (temp == 0)
					return target;
				if (temp<ClosestLength){
					ClosestLength = temp;
					ClosestTarget = sum;
				}	
			}
		}
	}
	return ClosestTarget;
}