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

For example, given array S = {-1 2 1 -4}, and target = 1.

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

• 与3Sum题的解法类似，加一层for循环即可。

• 维护一个2个数字和的hashMap，然后利用2sum去处理这个hashMap,即hashMap[sum1],hashMap[sum2],满足sum1 + sum2 == target;