leetcode 283[easy----Move Zeroes
难度：easy
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:
- You must do this in-place without making a copy of the array.
- Minimize the total number of operations.
思路：题目简单要求原位操作，不得出现 return. 将给定的list中的所有0移至list的最后。
先用while循环找到list中0出现的次数，然后删除所有的0.最后用for 循环在list最后补足删除的0。