最接近的三数之和

给定一个包括 n 个整数的数组 nums 和 一个目标值 target。找出 nums 中的三个整数，使得它们的和与 target 最接近。返回这三个数的和。假定每组输入只存在唯一答案。

例如，给定数组 nums = [-1，2，1，-4], 和 target = 1.

与 target 最接近的三个数的和为 2. (-1 + 2 + 1 = 2).

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {	
        int i = 0, j = 0, k = 0;
        int sum = 0, diff = 0, temp = 0;

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

        sum = nums[0] + nums[1] + nums[2];
        diff = abs(target - sum);
        for (i = 0; i < nums.size() - 2; i++) {
            j = i + 1;
            k = nums.size() - 1;
            while (j < k) {
                temp = nums[i] + nums[j] + nums[k];
                if (abs(temp - target) < diff) {
                    diff = abs(temp - target);
                    sum = temp;
                }
                if (temp < target) {
                    j++;
                }
                else if (temp > target) {
                    k--;
                }
                else if (temp == target)
                    return temp;
            }
        }
        return sum;
    }
};