LeetCode:3Sum Closet

probelms:

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).


Solution；依然同3Sun一样 先排序再左右夹逼  不同的是再加入一个变量mingap用来记录最小值

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        int result=0;
        int mingap=INT_MAX;  //无限宏
        
        sort(nums.begin(),nums.end());
        
        
        for(auto a=nums.begin();a!=prev(nums.end(),2);a++)
        {
            
            auto b=next(a);
            auto c=prev(nums.end());
            
            
            while(b<c)
            {
                const int sum=*a+*b+*c;
                const int gap=abs(sum-target);
                
                if(gap<mingap)
                {
                    result=sum;
                    mingap=gap;
                }
                
                if(sum<target) ++b;
                else --c;
            }
        }
        return result;
        
    }
};