What is a queue?

• Queue is a data structure that works on the principle of FIFO, First In First Out.
• So elements/tasks/items that enter the queue first, will be executed first.
• So, the entering priority matters a lot!
• First come, first serve basis.
• You can imagine a queue as a real-world example of people waiting in a queue to buy tickets for a movie!

Implementation of queue using list:

• So considering the above use cases, a list might be a good option to implement a queue. Also a lot of times, people use a list as a queue!

  Time Complexity

• Appending elements is O(1)
• Poping the first/oldest element is O(n) because the entire array has to be shifted.

Better solution for implementation of queue other than a list?

• collections.queue is the answer
• It uses LinkedList under the hood to implement a queue!

  Time Complexity

• Appending elements is O(1)
• Poping the first/oldest element is O(1)

Code example:

import collections

q = collections.deque([1, 2, 3])

# append element to the q
q.append(4)

# pop the first element from the q
q.popleft()

print(q)
# o/p: deque([2, 3, 4])

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The End!

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