解法一：
 

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