LeetCode 16 — 3Sum Closest(最接近的三数之和)

Given an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

Example:
Given array nums = [-1, 2, 1, -4], and target = 1.
The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

翻译
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).

分析
这题其实比3Sum还要简单，方法相同，由于只有一组解，所以不用考虑重复。

c++实现

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        int res = 0;
        int tmp = 0;
        if (nums.size() <= 3)
        {
            for (int i = 0; i < nums.size(); i++)
                res += nums[i];
            return res;
        }
        sort(nums.begin(),nums.end());
        res = nums[0]+nums[1]+nums[2];
        for (int i = 0; i < nums.size()-2; i++)
        {
            int j = i+1;
            int k = nums.size()-1;
            while (j < k)
            {
                tmp = nums[i]+nums[j]+nums[k];
                if (abs(target-tmp) <= abs(target-res))
                    res = tmp;
                if (tmp < target)
                    j++;
                else if (tmp > target)
                    k--;
                else
                    break;
            }
        }
        return res;
    }
};