class Solution {

    public void wiggleSort(int[] nums) {
        if (nums != null && nums.length == 0) return;
        Arrays.sort(nums);

        int[] arr = new int[nums.length];
        for (int i = 0; i < nums.length; i++) {
            arr[i] = nums[i];
        }

        int index1 = nums.length - 1, index2 = 0;

        int resIndex = 0;
        while (resIndex < nums.length) {

            if (resIndex % 2 == 0) {
                nums[resIndex] = arr[index1--];
                resIndex++;
            } else {
                nums[resIndex] = arr[index2++];
                resIndex++;
            }
        }
    }
}

class Solution {    

    public void wiggleSort(int[] nums) {
        int n = nums.length;
        for(int i = 1;i < n; i++){
            //如果是奇数，且小于前面的，或者如果是偶数，且大于前面的，那就要交换
            if(((i & 1) == 1 && nums[i] < nums[i-1])||((i &1) == 0 && nums[i] > nums[i-1])){
                int temp = nums[i];
                nums[i] = nums[i-1];
                nums[i-1] = temp;
            }
        }
    }
}