Lilly Tech Systems
LinkedList & Stack Problems
Master the fundamental pointer-based data structures that dominate coding interviews. From basic linked list traversal to monotonic stack patterns and combined challenges like LRU Cache — all with complete Python solutions, text diagrams, and complexity analysis.
Your Learning Path
Follow these lessons in order, or jump to any topic that interests you.
1. Fundamentals
LinkedList node structure, singly vs doubly linked lists, stack operations (push, pop, peek), and when to use each data structure.
2. LinkedList Basic Operations
5 problems: reverse a linked list, find middle element, detect cycle, merge two sorted lists, and remove duplicates.
3. LinkedList Advanced
5 problems: reverse nodes in K-group, copy list with random pointer, flatten multilevel doubly linked list, add two numbers, reorder list.
4. Stack Basic Problems
5 problems: valid parentheses, min stack, evaluate reverse Polish notation, daily temperatures, and asteroid collision.
5. Monotonic Stack
5 problems: next greater element, largest rectangle in histogram, maximal rectangle, stock span problem, and sum of subarray minimums.
6. Combined Patterns
4 problems combining linked lists and stacks: LRU cache, browser history, undo/redo system, and basic calculator.
7. Patterns & Tips
Pattern cheat sheet, pointer technique reference, common pitfalls, and FAQ accordion for linked list and stack interviews.
What You'll Learn
By the end of this course, you will be able to:
Master Pointer Manipulation
Confidently handle next/prev pointer rewiring, dummy nodes, fast/slow pointers, and recursive linked list solutions.
Stack Pattern Recognition
Instantly identify monotonic stack problems, parentheses matching, expression evaluation, and state-tracking patterns.
Solve Combined Problems
Build complex data structures like LRU Cache that combine hash maps, doubly linked lists, and stack-based undo systems.
Ace the Interview
Know the time/space complexity of every approach, handle edge cases, and communicate your thought process clearly.