1. 题目

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。

示例：
输入：nums = [-1,2,1,-4], target = 1
输出：2
解释：与 target 最接近的和是 2 (-1 + 2 + 1 = 2) 。
 
提示：
3 <= nums.length <= 10^3
-10^3 <= nums[i] <= 10^3
-10^4 <= target <= 10^4

2. 题解

import math
from typing import List


class Solution:
    def threeSumClosest(self, nums: List[int], target: int) -> int:
        res = math.inf
        n = len(nums)
        nums.sort()
        for first in range(n - 2):
            if first > 0 and nums[first] == nums[first -1]:
                continue
            second = first + 1
            third = n - 1
            while second < third:
                s = nums[first] + nums[second] + nums[third]
                if abs(s - target) < abs(res - target):
                    res = s
                if s > target:
                    third -= 1
                elif s < target:
                    second += 1
                else:
                    return target
        return res


if __name__ == "__main__":
    s = Solution()
    nums = [0,0,0]
    print(s.threeSum(nums, 1))