283. 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.

Note:

1. You must do this in-place without making a copy of the array.

2. Minimize the total number of operations.

My Solutions:

• extra-place的解法是Time: O(n); Space: O(n)

• in-place 解法：用一个pointer记录截止此处之前，全部数字都是已经替换成非0数字的index。然后再iterate一遍，把pointer之后到array结尾之前的数字变成0。

public void moveZeroes(int[] nums) {
    int len = nums.length;
    int pointer = 0;
    for (int i = 0; i < len; i++) {
        if (nums[i] != 0) {
            nums[pointer] = nums[i];
            pointer++;
        }
    }
    
    while (pointer != len) {
        nums[pointer] = 0; 
        pointer++;
    }
}