Leetcode-283题:Move Zeros

题目： 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：从左至右扫描，同时维护两个指针，p1指向最左边的0，p2指向p1右边的第一个非0，将p1和p2的元素交换，如果p2不存在则说明现在的序列已满足要求。

代码：

def moveZeroes(self, nums):
    """
    :type nums: List[int]
    :rtype: void Do not return anything, modify nums in-place instead.
    """
    if nums==None or len(nums)==0:
        return None
    p1 = 0
    while True:
        while p1<len(nums) and nums[p1] != 0:
            p1 += 1
        p2 = p1 + 1
        while p2<len(nums) and nums[p2]==0:
            p2 += 1
        if p2 >= len(nums):
            break
        else:
            nums[p1],nums[p2] = nums[p2],nums[p1]