Leetcode 283: Move Zeroes

283. Move Zeroes

  • Total Accepted: 127538
  • Total Submissions: 272915
  • Difficulty: Easy
  • Contributors: Admin

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.

 

Code

class Solution(object):
    def moveZeroes(self, nums):
        """
        :type nums: List[int]
        :rtype: void Do not return anything, modify nums in-place instead.
        """
        # maintain how many zeroes we have seen
        count0 = 0

        for idx, v in enumerate(nums):
            if v != 0:
                if count0 > 0:
                    nums[idx-count0] = v
                    nums[idx] = 0
            else:
                count0 += 1

 

Idea

An element should be moved count0 ahead, where count0 records how many zeroes we have seen.

 

If the order of non-zero elements is not required to maintain, we can have another algorithm:

class Solution(object):
    def moveZeroes(self, nums):
        """
        :type nums: List[int]
        :rtype: void Do not return anything, modify nums in-place instead.
        """
        
        start, end = 0, len(nums)-1
        while start < end:
            if nums[start] == 0:
                nums[start], nums[end] = nums[end], nums[start]
                end -= 1
            else:
                start += 1

 

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