HackMD
Stack Study Guide
Basic Stack Operations
Fundamental problems that introduce the concept and basic usage of stacks.
Practice Problems
- 🟨 71. Simplify Path [Solution]
- 🟨 394. Decode String
- 🟨 735. Asteroid Collision
- 🟥 895. Maximum Frequency Stack
Mathematical Operations and Expression Evaluation
Problems involving arithmetic operations and evaluating mathematical expressions using stacks.
Practice Problems
- 🟨 150. Evaluate Reverse Polish Notation [Solution]
- 🟥 224. Basic Calculator [Solution]
- 🟨 227. Basic Calculator II
Parentheses Matching and Processing
Problems that involve validating and manipulating strings with parentheses using stacks.
Practice Problems
- 🟩 20. Valid Parentheses [Solution]
- 🟥 32. Longest Valid Parentheses
- 🟨 1190. Reverse Substrings Between Each Pair of Parentheses [Solution]
Two Stacks
Problems that require the use of two stacks to solve efficiently.
Practice Problems
Monotonic Stack
Problems involving monotonic stacks, where elements are always sorted.
Practice Problems
Histogram and Interval Problems
A subset of monotonic stack problems dealing with histograms and intervals.
Practice Problems
- 🟥 84. Largest Rectangle in Histogram [Solution]
- 🟥 2334. Subarray With Elements Greater Than Varying Threshold [Solution]
Problem Difficulty Legend
- 🟩 Easy
- 🟨 Medium
- 🟧 Medium-Hard
- 🟥 Hard
- ⬛ Very Hard
