16. 3Sum Closest 又是一道先排序再双指针问题

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).

code

class Solution {public:    int threeSumClosest(vector<int>& nums, int target) {        sort(nums.begin(), nums.end());        int n = nums.size();        int positive  = INT_MAX, negative = INT_MAX;        for(int i = 0; i < n; i++){            int L = i + 1, R = n - 1;            int twoTarget = target - nums[i];            while(L < R){                                if(nums[L] + nums[R] > twoTarget){                    positive = min(positive, nums[L] + nums[R] - twoTarget);                    R--;                }else{                    negative = min(negative, twoTarget - nums[L] - nums[R]);                    L++;                }                                }                    }        if(positive > negative) return target - negative;        else return target + positive;    }};