283. Move Zeroes

Tags: #array #twopointers #easy

Problem Statement

Given an integer array nums, move all 0's to the end of it while maintaining the relative order of the non-zero elements.

Note that you must do this in-place without making a copy of the array.

Input: nums = [0,1,0,3,12]
Output: [1,3,12,0,0]

My Approach

class Solution:
    def moveZeroes(self, nums: List[int]) -> None:
        for i in nums:
            if i == 0:
                nums.remove(i)
                nums.append(i)

This was the first approach I thought of where we loop over the nums array once and if there is an element 0, we remove it and append it to the end of the list. However, I came up with another solution that gets rid of the loop.

class Solution:
    def moveZeroes(self, nums: List[int]) -> None:
        if 0 in nums:
            count = nums.count(0)
            nums[:] = [i for i in nums if i!= 0]
            nums.extend([0]*count)

In this solution, first we check if there's 0 or not in the nums array and if there is, we count the number of zero's in count. Then, we change the nums array in place by using list comprehension (Note: the nums[:] is required here since the default list comprehension would make a new array and point to that instead ) and remove all the zeros. Then using extend(), we add the zeros in the end, multipled by count for every zero we have.

Personal Thoughts

This is another hacky solution since I mostly utilised python methods and functionality. Will try to solve using a more conventional approach on a later date.