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:

1. You must do this in-place without making a copy of the array.
2. 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。