3Sum Closest 3个数字的和等于或者最接近与目标数

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).

class Solution {
public:
    int threeSumClosest(vector<int> &num, int target) {
        
        int len,i,left,right,min,ans,sum;
        sort(num.begin(),num.end());
        len=num.size();
        min=9999999;
        for(i=0;i<len-1;i++)
        {
            left=i+1;
            right=len-1;
            while(left<right)
            {
                sum=num[i]+num[left]+num[right];
                if(abs(target-sum)<min)
                {
                    min=abs(target-sum);
                    ans=sum;
                }
                if(sum<target)
                {
                    left++;
                }
                else if(sum>target){
                    right--;
                }
                else{
                    return sum;
                }
            }
        }
        return ans;
         
    }
};