Week 22 of 43
Core DSA
WEEK 22 LEARNING MODULE
Stacks, Queues & Monotonicity Fundamentals
Covers LIFO Stack and FIFO Queue mechanics, $O(1)$ operations with collections.deque, stack/queue cross-emulation, and Min Stack design.
4 Practice Problems4 Core ConceptsVerified Curriculum: high Confidence
What You'll Learn
- ✓Master LIFO Stack operations: `push()`, `pop()`, `peek()`, `is_empty()` in $O(1)$ time.
- ✓Master FIFO Queue operations: `enqueue()`, `dequeue()`, `front()`, `is_empty()` in $O(1)$ time.
- ✓Understand why Python `list.pop(0)` is $O(n)$ and utilize `collections.deque` for $O(1)$ operations.
- ✓Implement cross-structure emulation: queues using two stacks and stacks using queues.
- ✓Design a Min Stack supporting $O(1)$ `getMin()` retrieval.
Core Concepts
LIFO Stack Principle
O(1) all operationsLast In, First Out data structure; elements are inserted and removed from the same top end.
FIFO Queue Principle
O(1) all operationsFirst In, First Out data structure; elements are inserted at rear and removed from front.
Python `collections.deque`
O(1) both endsDoubly linked list-based queue supporting O(1) appends and pops from both ends.
Min Stack Auxiliary Tracking
O(1) time, O(n) spaceMaintaining a parallel minimum stack or storing (val, current_min) tuples to retrieve minimum in O(1).
Algorithms Covered
Parentheses Matching & Bracket ValidationQueue Simulation Using Two StacksStack Simulation Using QueueMin Stack State Tracking
Data Structures Applied
StacksQueuesDouble-Ended Queues (Deque)
“Be the one for the Queue not in the Queue”
— Kanika Sarna