11. 3Sum Closest
Given an integer array nums and an integer target, find three integers whose sum is closest to target.
Return the sum of the three integers. Each input has exactly one closest answer.
範例 1:
輸入： nums = [-1,2,1,-4], target = 1 輸出： 2
範例 2:
輸入： nums = [0,0,0], target = 1 輸出： 0
限制條件：
3 <= nums.length <= 500-1000 <= nums[i] <= 1000