wiggleSort.java

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

Example:

Input: nums = [3,5,2,1,6,4]
Output: One possible answer is [3,5,1,6,2,4]



The rule is:

		If i is even, nums[i] <= nums[i+1]
		If i is odd, nums[i] >= nums[i+1]

Traverse the array, and fix the ordering by swapping unmatched pairs.


//TC: O(N)
//SC: O(1)

class Solution {
public void wiggleSort(int[] nums) {
    boolean less = true;
    for (int i = 0; i < nums.length - 1; i++) {
        if (less) {
            if (nums[i] > nums[i + 1]) {
                swap(nums, i, i + 1);
            }
        } else {
            if (nums[i] < nums[i + 1]) {
                swap(nums, i, i + 1);
            }
        }
        less = !less;
    }
}
    
    private void swap(int[] nums, int i, int j) {
    int temp = nums[i];
    nums[i] = nums[j];
    nums[j] = temp;
}
}




SHORTER WAY, SAME LOGIC 

public void wiggleSort(int[] nums) {
    for (int i = 0; i < nums.length - 1; i++) {
        if (((i % 2 == 0) && nums[i] > nums[i + 1])
                || ((i % 2 == 1) && nums[i] < nums[i + 1])) {
            swap(nums, i, i + 1);
        }
    }
}