leetcode 324. Wiggle Sort II

Given an unsorted array nums, reorder it such that nums[0] < nums[1] > nums[2] < nums[3]....


Example:
(1) Given nums = [1, 5, 1, 1, 6, 4], one possible answer is [1, 4, 1, 5, 1, 6]. 
(2) Given nums = [1, 3, 2, 2, 3, 1], one possible answer is [2, 3, 1, 3, 1, 2].


Note:
You may assume all input has valid answer.


Follow Up:

Can you do it in O(n) time and/or in-place with O(1) extra space?

class Solution {
public:
	void wiggleSort(vector<int>& nums) {
		if(nums.empty())
			return;

		vector<int>aa=nums;
		sort(aa.begin(),aa.end());
		if(nums.size()%2!=0)
			for(int i=0;i<aa.size();)
			{
				nums[i]=aa[i/2];
				if(i+1<aa.size())
					nums[i+1]=aa[nums.size()/2+i/2+1];
				i+=2;
			}
		else
		{
			for(int i=0;i<aa.size();)
			{
				nums[i]=aa[i/2];
				if(i+1<aa.size())
				{
					nums[i+1]=aa[nums.size()/2+i/2];
				}
				i+=2;
			}
		}
		for(int i=2;i<nums.size()-1;)
		{
			if(nums[i-1]<=nums[i])
			{
				int tp=nums[i+1];
				nums[i+1]=nums[i-1];
				nums[i-1]=tp;
				i=2;
			}
			else if(nums[i+1]<=nums[i])
			{
				int tp=nums[i];
				nums[i]=nums[i-2];
				nums[i-2]=tp;
				i=2;
			}
			else
				i+=2;
		}
	}
};

accepted