[LeetCode] 283. Move Zeroes

 Problem : https://leetcode.com/problems/move-zeroes/

Use 2 pointers approach.  The slow pointer moves only when num != 0. The fast pointer moves every time. 

Time Complexity = O ( N )

class Solution:
    def moveZeroes(self, nums: List[int]) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        
        i = j = 0
        
        while j < len(nums):
            if nums[j] != 0:
                nums[i] = nums[j]
                i += 1
            
            j += 1
            
        while i < len(nums):
            nums[i] = 0
            i += 1

Another solution similar to bubble-sort. Time Complexity = O ( N ** 2 )

class Solution:
    def moveZeroes(self, nums: List[int]) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        
        i = 0
        N = len(nums)
        
        while i < N:
            if nums[i] != 0:
                i += 1
                continue

            j = i
            while j + 1 < N:
                nums[j], nums[j+1] = nums[j+1], nums[j]
                j += 1
            
            N -= 1