LeetCode_3 sum closet

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).

3 sum 的变形，这里不需要考虑重复而已

class Solution {

public:

    int threeSumClosest(vector<int> &num, int target) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        sort(num.begin(), num.end());

        int len = num.size();

        if(len < 3) return 0;

        int res = num[0] + num[1] + num[2];

        for(int i = 0; i <= len -3; ++i){

            

            int low = i+1;

            int high = len -1;

            while(low < high){

                

                int sum = num[i] + num[low] + num[high];

                if(sum == target)

                    return target;

                else if(sum < target){

                    ++low;

                    if(abs(sum - target) < abs(res - target))

                        res = sum;

                }else{

                    --high;

                    if(abs(sum - target) < abs(res - target))

                        res = sum;



                }

            }

        }

        

        return res;

    }

};