Given an arraynums, write a function to move all0's to the end of it while maintaining the relative order of the non-zero elements.

For example, givennums = [0, 1, 0, 3, 12], after calling your function,numsshould be[1, 3, 12, 0, 0].

Note:

1. You must do this in-place without making a copy of the array.
2. Minimize the total number of operations.

Credits:
Special thanks to@jianchao.li.fighterfor adding this problem and creating all test cases.

class Solution {
    public void moveZeroes(int[] nums) {
        if (nums == null || nums.length == 0) return;

        int i = 0;
        while (i < nums.length && nums[i] != 0){
            i++;
        }

        int j = i;
        while (j < nums.length){
            if (nums[j] != 0){
                swap(nums, i, j);
                i++;
            }
            j++;
        }
    }

    private void swap(int[] nums, int i, int j){
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }
}