DSA · Theory

Double Ended Priority Queue

Theory

308/810

Double Ended Priority Queue

Double Ended Priority Queue is a DSA topic. In plain words you use it for print jobs in a lab printer. Don’t start with a slogan — start with that picture.

Smallest example: enqueue / dequeue FIFO. Type it, run it, and say what you see. If you can do that from memory, you know Double Ended Priority Queue.

From the example next to this theory — Double Ended Priority Queue — queue is FIFO.

Trap — confusing front and rear. Fix that before you talk about advanced DSA.

Viva — what is Double Ended Priority Queue? Then show enqueue / dequeue FIFO. Then name the trap.

Diagram

  front → [A][B][C] ← rear
  out ↑         ↑ in
       FIFO

Exam tip

What is Double Ended Priority Queue? Show this: enqueue / dequeue FIFO. Trap: confusing front and rear.

Example

from collections import deque

q = deque()
q.append(10)      # enqueue
q.append(20)
print(q.popleft())  # 10
print(list(q))

Double Ended Priority Queue — queue is FIFO. deque.popleft() is O(1).

Short notes

DefDouble Ended Priority Queue — print jobs in a lab printer.
Ruleenqueue / dequeue FIFO
Trapconfusing front and rear
Usea lab printer

DSA · Theory

Double Ended Priority Queue

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Theory

308/810

Double Ended Priority Queue

Double Ended Priority Queue is a DSA topic. In plain words you use it for print jobs in a lab printer. Don’t start with a slogan — start with that picture.

Smallest example: enqueue / dequeue FIFO. Type it, run it, and say what you see. If you can do that from memory, you know Double Ended Priority Queue.

From the example next to this theory — Double Ended Priority Queue — queue is FIFO.

Trap — confusing front and rear. Fix that before you talk about advanced DSA.

Viva — what is Double Ended Priority Queue? Then show enqueue / dequeue FIFO. Then name the trap.

Diagram

  front → [A][B][C] ← rear
  out ↑         ↑ in
       FIFO

Exam tip

What is Double Ended Priority Queue? Show this: enqueue / dequeue FIFO. Trap: confusing front and rear.

Example

from collections import deque

q = deque()
q.append(10)      # enqueue
q.append(20)
print(q.popleft())  # 10
print(list(q))

Double Ended Priority Queue — queue is FIFO. deque.popleft() is O(1).

Short notes

DefDouble Ended Priority Queue — print jobs in a lab printer.
Ruleenqueue / dequeue FIFO
Trapconfusing front and rear
Usea lab printer

Double Ended Priority Queue

Example

Short notes

Questions

Double Ended Priority Queue

Example

Short notes

Questions