Array - 508. Wiggle Sort

508. Wiggle Sort

Given an unsorted array nums, reorder it in-place such that

nums[0] <= nums[1] >= nums[2] <= nums[3]....

Example

Example 1:

Input: [3, 5, 2, 1, 6, 4]
Output: [1, 6, 2, 5, 3, 4]
Explanation: This question may have multiple answers, and [2, 6, 1, 5, 3, 4] is also ok.

Example 2:

Input: [1, 2, 3, 4]
Output: [2, 1, 4, 3]

Notice

Please complete the problem in-place.

思路：

仔细分析输出数组，可以发现下标索引为奇数的数是极大值点，下标索引是偶数的是极小值点，只要遍历数组的时候，移动相邻两个数，就可以。

代码：

java：

public class Solution {
    /*
     * @param nums: A list of integers
     * @return: nothing
     */
    public void wiggleSort(int[] nums) {
        if (nums == null || nums.length <= 1) return;
        
        for (int i = 1; i < nums.length; i++) {
            if (i % 2 == 1){
                if (nums[i - 1] > nums[i]) swap(nums, i - 1, i);
            } else {
                if (nums[i - 1] < nums[i]) swap(nums, i - 1, i);
            }
        }
        
    }
    
    private void swap(int[] nums, int i, int j ){
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }
    
}