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Queues

Import packages

from collections import deque

deque is a double-ended queue that allows you to efficiently add and remove elements from both ends.

queue = deque()
queue

deque([])

Add an element to the right side - O(1)

queue.append(1)
queue.append(2)

queue

deque([1, 2])

Dequeue an element from the left side - O(1)

If simply using pop() it will act as a stack, removing the last element added (LIFO).

queue.popleft()

1

Peek at the leftmost element without removing it - O(1)

queue[-1]

2