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# Move all zeroes to end of array using List Comprehension in Python

Given an array of random numbers, Push all the zeros of a given array to the end of the array. For example, if the given arrays is {1, 9, 8, 4, 0, 0, 2, 7, 0, 6, 0}, it should be changed to {1, 9, 8, 4, 2, 7, 6, 0, 0, 0, 0}. The order of all other elements should be same. Expected time complexity is O(n) and extra space is O(1). Examples:

```Input :  arr = [1, 2, 0, 4, 3, 0, 5, 0]
Output : arr = [1, 2, 4, 3, 5, 0, 0, 0]

Input : arr  = [1, 2, 0, 0, 0, 3, 6]
Output : arr = [1, 2, 3, 6, 0, 0, 0]```

We have existing solution for this problem please refer Move all zeroes to end of array link. We will solve this problem in python using List Comprehension in a single line of code.

Implementation:

## Python

 `# Function to append all zeros at the end``# of array``def` `moveZeros(arr):``    ` `    ``# first expression returns a list of``    ``# all non zero elements in arr in the``    ``# same order they were inserted into arr``    ``# second expression returns a list of``    ``# zeros present in arr``    ``return` `[nonZero ``for` `nonZero ``in` `arr ``if` `nonZero!``=``0``] ``+` `\``        ``[Zero ``for` `Zero ``in` `arr ``if` `Zero``=``=``0``]` `# Driver function``if` `__name__ ``=``=` `"__main__"``:``    ``arr ``=` `[``1``, ``2``, ``0``, ``4``, ``3``, ``0``, ``5``, ``0``]``    ``print` `(moveZeros(arr))`

Output

`[1, 2, 4, 3, 5, 0, 0, 0]`

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#### Approach#2: Using while loop

This approach moves all zeroes in an input array to the end of the array while keeping the non-zero elements in their original order. It uses two pointers to keep track of the positions of the zeroes and non-zeroes in the array, and swaps them as necessary.

#### Algorithm

1. Initialize two pointers i and j to 0.
2. Traverse the array with j and for each non-zero element, swap arr[i] and arr[j] and increment i.
3. Return the resulting array.

## Python3

 `def` `move_zeroes(arr):``    ``i, j ``=` `0``, ``0``    ``while` `j < ``len``(arr):``        ``if` `arr[j] !``=` `0``:``            ``arr[i], arr[j] ``=` `arr[j], arr[i]``            ``i ``+``=` `1``        ``j ``+``=` `1``    ``return` `arr``arr``=``[``1``, ``2``, ``0``, ``4``, ``3``, ``0``, ``5``, ``0``]``print``(move_zeroes(arr))`

Output

`[1, 2, 4, 3, 5, 0, 0, 0]`

Time Complexity: O(n)
Auxiliary Space: O(1)