Given an unsorted array nums, reorder it in-place such that
nums[0] <= nums[1] >= nums[2] <= nums[3]....
Notice
Please complete the problem in-place.
Example
Given nums = [3, 5, 2, 1, 6, 4], one possible answer is [1, 6, 2, 5, 3, 4].
原文：http://www.cnblogs.com/grandyang/p/5500067.html