16\. 3Sum Closest

Medium

Given an integer array `nums` of length `n` 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 1:**

**Input:** nums = [-1,2,1,-4], target = 1

**Output:** 2

**Explanation:** The sum that is closest to the target is 2. (-1 + 2 + 1 = 2). 

**Example 2:**

**Input:** nums = [0,0,0], target = 1

**Output:** 0 

**Constraints:**

*   `3 <= nums.length <= 1000`
*   `-1000 <= nums[i] <= 1000`
*   <code>-10<sup>4</sup> <= target <= 10<sup>4</sup></code>