Wiggle Sort

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

For example, given nums = [3, 5, 2, 1, 6, 4], one possible answer is [1, 6, 2, 5, 3, 4].

    public void wiggleSort(int[] nums) {

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

        }
    }

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].

Not a good solution, time O(nlogn), space O(n)...

public void wiggleSort(int[] nums) {
    if(nums.length < 2)
        return;
    Arrays.sort(nums);
    int[] first = Arrays.copyOfRange(nums, 0, (nums.length + 1) / 2),
        second = Arrays.copyOfRange(nums, (nums.length + 1) / 2, nums.length);
    int i = first.length - 1, j = second.length - 1; 
    for(int k = 0; k < nums.length; k ++){
        if((k & 1) == 0){
            nums[k] = first[i --];
        }else {
            nums[k] = second[j --];
        }
    }
}