一个vector里3个数加在一起离target最近的值。Two Pointers

16. 3Sum Closest.cpp

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        int res = target + 1000;
        sort(nums.begin(),nums.end());
        for (int i=0;i<nums.size()-2;i++){
            int target2 = target - nums[i];
            int j=i+1;
            int k=nums.size()-1;
            while (j<k){
                if (abs(nums[j]+nums[k]-target2)<abs(res-target)){
                    res = nums[j]+nums[k]+nums[i];
                }
                if (nums[j]+nums[k] > target2) k--;
                else if (nums[j]+nums[k] < target2) j++;
                else return target;
            }
        }
        return res;
    }
};