leetcode 016 —— 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).

思路：设定closest，closest与target差值最小，类似贪心算法

class Solution {public:int threeSumClosest(vector<int>& nums, int target) {int n = nums.size();if (n < 3) return 0;int closest = nums[0]+nums[1]+nums[2];sort(nums.begin(), nums.end());for (int i = 0; i < n-2; i++){if (i>0 && nums[i] == nums[i - 1])continue;int l = i + 1;int r = n - 1;while (l < r){int sum = nums[i] + nums[l] + nums[r];if (sum == target)return sum;else if(sum>target){closest = (abs(closest - target) < abs(sum - target) ? closest : sum);r--;}else{closest = (abs(closest - target) < abs(sum - target) ? closest : sum);l++;}}}return closest;}};