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:

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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]