Move Zeroes

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should 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.

Solution: 把非零数往前移，后面用零补齐。
Time complexity is O(n), constant space.

public class Solution {
    public void moveZeroes(int[] nums) {
        if (nums == null || nums.length <= 1) {
            return;
        }
        
        int position = 0;
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] != 0) {
                nums[position] = nums[i];
                position++;
            }
        }
        
        for (int i = position; i < nums.length; i++) {
            nums[i] = 0;
        }
    }
}