LeetCode Wiggle Sort II

原题链接在这里：https://leetcode.com/problems/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?

Credits:
Special thanks to @dietpepsi for adding this problem and creating all test cases.

 

Time Complexity: O(n*logn). Space: O(n).

AC Java:

 1 public class Solution {
 2     public void wiggleSort(int[] nums) {
 3         if(nums == null || nums.length == 0){
 4             return;
 5         }
 6         
 7         Arrays.sort(nums);
 8         int len = nums.length;
 9         int mid = (len-1)/2 + 1;
10         int right = len;
11         int [] temp = new int[len];
12         for(int i = 0; i<len; i++){
13             temp[i] = i%2 == 0 ? nums[--mid] : nums[--right];
14         }
15         for(int i = 0; i<len; i++){
16             nums[i] = temp[i];
17         }
18     }
19 }