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

Given array nums = [-1, 2, 1, -4], and target = 1.

The sum that is closest to the target is 2.

给定⼀个数组，要求在这个数组中找出 3 个数之和离 target 最近。