Python List Comprehension | Segregate 0’s and 1’s in an array list

You are given an array of 0s and 1s in random order. Segregate 0s on left side and 1s on right side of the array. 

Examples:

Input  :  arr = [0, 1, 0, 1, 0, 0, 1, 1, 1, 0] 
Output :  [0, 0, 0, 0, 0, 1, 1, 1, 1, 1] 

We have existing solution for this problem please refer Segregate 0s and 1s in an array link. We can solve this problem quickly in Python using List Comprehension. Traverse given list and separate out two different lists, one contains all 0’s and another one contains all 1’s. Now concatenate both lists together. 

Python3

# Function to Segregate 0's and 1's in an array list


def segregate(arr):
    res = ([x for x in arr if x == 0] + [x for x in arr if x == 1])
    print(res)


# Driver program
if __name__ == "__main__":
    arr = [0, 1, 0, 1, 0, 0, 1, 1, 1, 0]
    segregate(arr)

Output

[0, 0, 0, 0, 0, 1, 1, 1, 1, 1]

Time complexity: O(n), where n is the length of the input array, as the code needs to traverse the entire input array to segregate 0’s and 1’s.
Auxiliary space: O(n), as the code creates a new result array of the same length as the input array.

Method : Using count() method

Python3

# Function to Segregate 0's and 1's in an array list

def segregate(arr):
    res = ([0]*arr.count(0) + [1]*arr.count(1))
    print(res)

# Driver program
if __name__ == "__main__":
    arr = [0, 1, 0, 1, 0, 0, 1, 1, 1, 0]
    segregate(arr)

Output

[0, 0, 0, 0, 0, 1, 1, 1, 1, 1]

Time complexity: O(n), where n is the length of the input array.
Auxiliary space: O(n), as we are creating a new list with the segregated elements.