DSA · Theory

Priority Queue using Doubly Linked List

Theory

603/810

Priority Queue using Doubly Linked List

Priority Queue using Doubly Linked List is a DSA topic. In plain words you use it for a ticket queue node in a counter. Don’t start with a slogan — start with that picture.

Smallest example: head → next → …. Type it, run it, and say what you see. If you can do that from memory, you know Priority Queue using Doubly Linked List.

From the example next to this theory — Priority Queue using Doubly Linked List — queue is FIFO.

Trap — losing the next pointer on delete. Fix that before you talk about advanced DSA.

Viva — what is Priority Queue using Doubly Linked List? Then show head → next → …. Then name the trap.

Diagram

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

Exam tip

What is Priority Queue using Doubly Linked List? Show this: head → next → …. Trap: losing the next pointer on delete.

Example

from collections import deque

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

Priority Queue using Doubly Linked List — queue is FIFO. deque.popleft() is O(1).

Short notes

DefPriority Queue using Doubly Linked List — a ticket queue node in a counter.
Rulehead → next → …
Traplosing the next pointer on delete
Usea counter

DSA · Theory

Priority Queue using Doubly Linked List

← All stacks

Theory

603/810

Priority Queue using Doubly Linked List

Priority Queue using Doubly Linked List is a DSA topic. In plain words you use it for a ticket queue node in a counter. Don’t start with a slogan — start with that picture.

Smallest example: head → next → …. Type it, run it, and say what you see. If you can do that from memory, you know Priority Queue using Doubly Linked List.

From the example next to this theory — Priority Queue using Doubly Linked List — queue is FIFO.

Trap — losing the next pointer on delete. Fix that before you talk about advanced DSA.

Viva — what is Priority Queue using Doubly Linked List? Then show head → next → …. Then name the trap.

Diagram

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

Exam tip

What is Priority Queue using Doubly Linked List? Show this: head → next → …. Trap: losing the next pointer on delete.

Example

from collections import deque

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

Priority Queue using Doubly Linked List — queue is FIFO. deque.popleft() is O(1).

Short notes

DefPriority Queue using Doubly Linked List — a ticket queue node in a counter.
Rulehead → next → …
Traplosing the next pointer on delete
Usea counter

Priority Queue using Doubly Linked List

Example

Short notes

Questions

Priority Queue using Doubly Linked List

Example

Short notes

Questions