Implement Stack Using Two Queues — Two Approaches Explained
Implement a stack using two queues with costly push and costly pop approaches. Complete Python solutions with complexity analysis.
·4 min read · #dsa#stacks#queues
#stacks
36 posts · page 1 of 1
132 Pattern — Monotonic Stack with Reverse Traversal (LeetCode 456)
Solve the 132 Pattern problem using a monotonic stack scanning right to left. Python solution tracking s3 candidates and s2 maximum, with detailed trace.
·7 min read · #dsa#stacks#advanced
Asteroid Collision Problem Using Stacks
Solve the asteroid collision problem (LeetCode 735) using a stack. Covers collision rules, Python implementation, and all edge cases.
·3 min read · #dsa#stacks#intermediate
Basic Calculator I, II, III — Complete Expression Evaluation Guide
Solve Basic Calculator problems LeetCode 224, 227, and 772. Master stack-based expression evaluation with +, -, *, /, and parentheses in Python.
·6 min read · #dsa#stacks#advanced
Car Fleet Problem — Stack-Based Arrival Time Solution
Solve LeetCode 853 Car Fleet using a stack. Sort by position, compare arrival times, and count fleets. Python solution with visual trace.
·5 min read · #dsa#stacks#sorting
The Celebrity Problem Using Stack-Based Elimination
Solve the celebrity problem in O(n) time using a stack elimination technique. Includes proof of correctness, Python code, and matrix examples.
·4 min read · #dsa#stacks#intermediate
Decode String (LeetCode 394) — Nested Bracket Decoding
Decode nested encoded strings like '3[a2[c]]' using a stack. Complete walkthrough with Python solution, traces, and edge cases.
·3 min read · #dsa#stacks#intermediate
Evaluate Reverse Polish Notation — Stack Solution Explained
Solve LeetCode 150 Evaluate Reverse Polish Notation using a stack. Python implementation with division gotcha, traces, and complexity analysis.
·5 min read · #dsa#stacks#intermediate
Exclusive Time of Functions — Call Stack Simulation (LeetCode 636)
Solve Exclusive Time of Functions with a stack simulating a call stack. Python solution with timestamps, detailed trace, and edge case handling.
·6 min read · #dsa#stacks#intermediate
Implement Queue Using Two Stacks — Amortized O(1) Solution
Implement a queue using two stacks with amortized O(1) operations. Covers costly enqueue vs costly dequeue approaches with Python code.
·5 min read · #dsa#stacks#queues
Flatten Nested List Iterator — Lazy Stack Design (LeetCode 341)
Design a Flatten Nested List Iterator using a stack for lazy flattening. Python solution with iterator protocol, step-by-step trace, and design analysis.
·6 min read · #dsa#stacks#design
Largest Rectangle in Histogram Using Stack
Find the largest rectangle in a histogram using a monotonic stack in O(n). Detailed walkthrough, Python code, visual trace, and common pitfalls.
·4 min read · #dsa#stacks#advanced
Minimum Remove to Make Valid Parentheses — Stack Solution
Solve LeetCode 1249 Minimum Remove to Make Valid Parentheses using a stack. Two-pass and one-pass approaches with Python code and traces.
·5 min read · #dsa#stacks#strings
Maximal Rectangle in Binary Matrix
Find the maximal rectangle containing only 1s in a binary matrix. Builds on the largest rectangle in histogram technique with detailed explanation.
·3 min read · #dsa#stacks#advanced
Maximum Frequency Stack — HashMap + Stack Groups (LeetCode 895)
Maximum Frequency Stack solved with HashMap and stack groups by frequency. Python implementation with step-by-step trace, complexity analysis, and design insights.
·6 min read · #dsa#stacks#design
Next Greater Element II — Circular Array with Monotonic Stack (LeetCode 503)
Next Greater Element II solved with monotonic stack and circular array double-length trick. Python solution with step-by-step trace, complexity analysis, and patterns.
·7 min read · #dsa#stacks#monotonic-stack
Online Stock Span — Class Design with Stack
Design an Online Stock Span class (LeetCode 901) using a stack. Covers amortized analysis, Python implementation, and the price-span pair technique.
·3 min read · #dsa#stacks#intermediate
Next Smaller Element Using Stack — Monotonic Increasing Stack Pattern
Solve the Next Smaller Element problem with a monotonic increasing stack in O(n). Python code, step-by-step trace, and reusable pattern for interviews.
·6 min read · #dsa#stacks#intermediate
Stack and Queue Interview Patterns — 15+ Patterns Catalog
Comprehensive catalog of 15+ stack and queue interview patterns with when-to-use guide, Python templates, complexity analysis, and problem mapping for coding interviews.
·9 min read · #dsa#stacks#queues
Remove Duplicate Letters — Monotonic Stack + Greedy Solution
Solve LeetCode 316 Remove Duplicate Letters using monotonic stack with frequency and visited tracking. Smallest lexicographic subsequence in Python.
·5 min read · #dsa#stacks#greedy
Detect Redundant Parentheses Using a Stack
Learn to detect redundant parentheses in expressions using a stack. Covers the algorithm, Python implementation, and edge cases with traces.
·3 min read · #dsa#stacks#intermediate
Real-World Applications of Stacks and Queues — From Undo/Redo to BFS Crawlers
Real-world applications of stacks and queues: undo/redo systems, browser history, call stacks, task scheduling, message queues, and BFS web crawlers with Python examples.
·7 min read · #dsa#stacks#queues
Remove K Digits to Make Smallest Number
Use a monotonic stack to remove k digits from a number to make it as small as possible. LeetCode 402 solution with Python code and traces.
·4 min read · #dsa#stacks#intermediate
Simplify Unix Path Using a Stack — LeetCode 71 Solution
Solve Simplify Path LeetCode 71 with a stack. Handle ., .., multiple slashes, and edge cases. Python solution with step-by-step trace.
·4 min read · #dsa#stacks#strings
Score of Parentheses — Stack-Based Scoring (LeetCode 856)
Solve Score of Parentheses using a stack to track nested scores. Python solution with trace, O(n) time, plus the bit-shift trick for O(1) space.
·6 min read · #dsa#stacks#intermediate
Sort a Stack Using Another Stack
Learn how to sort a stack using only one additional stack. Step-by-step trace, Python implementation, and O(n²) complexity analysis.
·3 min read · #dsa#stacks#intermediate
Tag Validator — Stack-Based XML Parsing (LeetCode 591)
Tag Validator solved with stack-based HTML/XML tag matching and CDATA parsing. Python solution with edge cases, step-by-step trace, and complexity analysis.
·6 min read · #dsa#stacks#strings
Stock Span Problem Using Stacks
Solve the stock span problem efficiently using a monotonic stack. Includes brute force vs optimal approach, Python code, and visual trace.
·4 min read · #dsa#stacks#intermediate
Sum of Subarray Minimums — Contribution Technique with Stack (LeetCode 907)
Solve Sum of Subarray Minimums using the contribution technique with monotonic stacks. Python solution with modular arithmetic, traces, and O(n) analysis.
·7 min read · #dsa#stacks#advanced
Trapping Rain Water Using Stack — Step-by-Step Stack Approach Explained
Solve Trapping Rain Water (LeetCode 42) using a stack-based approach. Python code with detailed trace, comparison with two-pointer, and complexity analysis.
·6 min read · #dsa#stacks#advanced
Validate Stack Sequences — Simulate Push/Pop (LeetCode 946)
Validate Stack Sequences solved by simulating push and pop operations. Python solution with step-by-step trace, edge cases, and complexity analysis for LeetCode 946.
·6 min read · #dsa#stacks#simulation
Stack-Based Parsing: Parentheses, Decode String & Calculator
Master stack-based parsing patterns — balanced parentheses, minimum removals, longest valid parentheses, decode string, and basic calculator with Python solutions.
·9 min read · #dsa#stacks#intermediate
Stack Expression Evaluation: Infix, Postfix & Calculator
Build a calculator from scratch — learn infix, prefix, and postfix notation, the Shunting Yard algorithm, postfix evaluation, and Python implementation.
·8 min read · #dsa#stacks#intermediate
Stack Next Greater Element & Monotonic Stacks
Master the monotonic stack pattern — solve Next Greater Element, Next Smaller, stock span, and circular array variants with Python templates and visual walkthroughs.
·9 min read · #dsa#stacks#intermediate
Stacks and Queues in DSA
A practical introduction to stacks and queues — LIFO vs FIFO, using a Python list as a stack, collections.deque as a queue, and the real-world problems each one solves cleanly.
·10 min read · #dsa#stacks#queues
Stacks & Queues: 8 Practice Problems with Solutions
Eight classic stack and queue interview problems with worked Python solutions — Valid Parentheses, Min Stack, Daily Temperatures, Sliding Window Maximum, and more.
·10 min read · #dsa#stacks#queues