LeetCode - Move Zeros

 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.

簡單來說題目要求我們在一個array中遇到0的整數時候必須往最右邊移動
而且不可以改變大於0的整數元素之間的排序關係(這點我一直搞錯，害我以為要做sort)

自己寫的解法如下