Deque Design Patterns — Sliding Window, Palindrome, Work Stealing
Master deque design patterns including sliding window maximum, palindrome checking, work stealing, and BFS/DFS hybrid. Python implementations.
·7 min read · #dsa#queues#deque
#advanced
98 posts · page 1 of 3
Priority Queue Patterns — Top-K, Merge K Lists, Median, Dijkstra
Master priority queue patterns for coding interviews. Top-K elements, merge K sorted lists, running median, and Dijkstra's algorithm in Python.
·7 min read · #dsa#heaps#priority-queue
Design Front Middle Back Queue — Two Deques (LeetCode 1670)
Design Front Middle Back Queue using two balanced deques. Python solution with O(1) operations, step-by-step trace, and complexity analysis for LeetCode 1670.
·6 min read · #dsa#queues#design
Open the Lock — BFS on State Space (LeetCode 752)
Open the Lock problem solved with BFS on 4-digit state space. Python solution with deadend handling, bidirectional BFS optimization, and complexity analysis.
·6 min read · #dsa#queues#bfs
Sliding Window Maximum Using Deque
Solve the sliding window maximum problem in O(n) using a monotonic deque. Covers the algorithm, Python code, visual traces, and variations.
·4 min read · #dsa#queues#advanced
Shortest Subarray with Sum at Least K — Monotonic Deque (LeetCode 862)
Shortest Subarray with Sum at Least K solved with monotonic deque and prefix sums. Python solution with detailed trace, complexity analysis, and edge cases.
·7 min read · #dsa#queues#deque
Task Scheduler — Queue + Heap Approach
Solve the Task Scheduler problem (LeetCode 621) using a queue and max-heap. Covers the greedy formula and simulation approaches with Python code.
·3 min read · #dsa#queues#advanced
Zigzag Level Order Traversal — BFS with Deque in Python
Zigzag level order traversal of a binary tree using BFS and deque. Step-by-step Python solution with visual trace, complexity analysis, and interview tips.
·5 min read · #dsa#queues#trees
Word Ladder BFS Approach — Shortest Transformation Sequence
Word Ladder solved with BFS and pattern matching optimization. Step-by-step Python solution for LeetCode 127 with complexity analysis and interview tips.
·6 min read · #dsa#queues#bfs
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
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
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
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
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
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
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
Alien Dictionary: Topological Sort from Word Ordering
Derive character ordering from sorted alien words using topological sort, with course schedule variants and prerequisite chain problems.
·10 min read · #dsa#graphs#advanced
Detecting Negative Cycles in Graphs
Learn how to detect negative cycles using Bellman-Ford's nth relaxation, SPFA algorithm, and apply it to arbitrage detection in currency exchange graphs.
·14 min read · #dsa#graphs#advanced
Word Search, Boggle Solver, and Word Ladder: Grid + String Graph Problems
Solve word search with DFS backtracking, Boggle with Trie pruning, and word ladder with BFS for efficient string transformation problems.
·11 min read · #dsa#graphs#advanced
Skip List: A Probabilistic Alternative to Balanced Trees
Understand skip lists — multi-level linked lists with probabilistic balancing that achieve O(log n) search, insert, and delete. Covers the concept, comparison with BSTs, Redis use case, and full Python implementation.
·15 min read · #dsa#advanced#intermediate
String Hashing Techniques for Pattern Matching
Master string hashing for pattern matching — polynomial hashing, rolling hash for Rabin-Karp, double hashing, repeated DNA sequences, and longest duplicate substring.
·15 min read · #dsa#strings#advanced
A* Search Algorithm: Heuristic Pathfinding Explained
Learn the A* search algorithm with f=g+h, admissible heuristics, grid pathfinding, and Python implementation compared to Dijkstra and BFS.
·12 min read · #dsa#graphs#advanced
Articulation Points and Bridges in Graphs
Find critical nodes and edges in graphs using Tarjan's algorithm with discovery and low-link arrays, with Python code and network applications.
·10 min read · #dsa#graphs#advanced
Backtracking Comprehensive: From Template to Hard Problems
Master backtracking with the choose-explore-unchoose template. Solve N-Queens, Sudoku, word search, generate parentheses, palindrome partitioning, and subset sum.
·12 min read · #dsa#backtracking#advanced
Binary Lifting for LCA and Kth Ancestor Queries
Master binary lifting to answer Lowest Common Ancestor (LCA) and kth ancestor queries in O(log n) with O(n log n) preprocessing. Full Python implementations with tree examples.
·11 min read · #dsa#trees#advanced
Bitmask DP: Subsets, TSP, and Assignment Problems
Master bitmask dynamic programming — represent subsets as integers, solve the Travelling Salesman Problem, assignment problem, and subset enumeration with Python implementations.
·13 min read · #dsa#dynamic-programming#advanced
Counting Problems and Combinatorics in DSA
Master counting techniques for DSA: permutations, combinations, Pascal's triangle, Catalan numbers, inclusion-exclusion, pigeonhole principle, and modular arithmetic.
·16 min read · #dsa#math#advanced
DP on Trees: From Max Independent Set to Rerooting
Master dynamic programming on trees — max independent set, tree diameter via DP, House Robber III, rerooting technique, and post-order traversal patterns with Python implementations.
·15 min read · #dsa#dynamic-programming#advanced
Euler Path and Circuit: Hierholzer's Algorithm
Understand Euler paths, circuits, and Hamiltonian differences with Hierholzer's algorithm, degree conditions, and Python implementations.
·12 min read · #dsa#graphs#advanced
Graph Coloring: Algorithms and Real-World Applications
Learn graph coloring with greedy coloring, bipartite check via 2-coloring, m-coloring with backtracking, and applications in scheduling.
·12 min read · #dsa#graphs#advanced
LRU Cache Design: HashMap + Doubly Linked List
Design and implement an LRU Cache from scratch using a HashMap and Doubly Linked List for O(1) get and put, with Python code, OrderedDict shortcut, and real-world context.
·8 min read · #dsa#design#advanced
Network Flow: Ford-Fulkerson and Edmonds-Karp
Understand max flow, residual graphs, augmenting paths, Ford-Fulkerson, Edmonds-Karp, and the max-flow min-cut theorem with Python code.
·12 min read · #dsa#graphs#advanced
Randomized Algorithms: QuickSelect, Reservoir Sampling, and Beyond
Explore randomized algorithms -- QuickSelect for O(n) kth element, reservoir sampling for streams, randomized quicksort, skip lists, bloom filters, and Monte Carlo vs Las Vegas classification.
·14 min read · #dsa#algorithms#advanced
Red-Black Trees Explained: Rules, Rotations & Real-World Usage
Understand Red-Black trees — the 5 rules, insertion cases, color flips, rotations, comparison with AVL, and why Java TreeMap and Linux use them.
·11 min read · #dsa#trees#advanced
Sqrt Decomposition and Mo's Algorithm
Learn sqrt decomposition for O(sqrt(n)) range queries and updates, plus Mo's algorithm for answering offline queries efficiently. Full Python implementations included.
·11 min read · #dsa#range-queries#advanced
Sparse Table for Range Queries in O(1)
Master sparse tables for O(1) range minimum/maximum queries with O(n log n) preprocessing. Learn construction, idempotent functions, and when to use sparse tables over segment trees.
·13 min read · #dsa#range-queries#advanced
Strongly Connected Components: Kosaraju and Tarjan
Master SCCs with Kosaraju's two-pass DFS and Tarjan's low-link algorithm, including condensation graphs and real applications in Python.
·11 min read · #dsa#graphs#advanced
Suffix Arrays: Construction, LCP, and Applications
Learn suffix arrays from scratch -- naive and O(n log^2 n) construction, LCP arrays, pattern searching with binary search, and applications like longest repeated substring.
·12 min read · #dsa#strings#advanced
Dimensional Modeling Deep Dive — The Kimball Way
Master Kimball dimensional modeling: fact table types, advanced dimension techniques, the bus matrix, grain decisions, and a complete e-commerce example.
·12 min read · #data-engineering#dimensional-modeling#data-warehouse
Advanced DP Patterns: Bitmask, Digit, Trees & Intervals
Master advanced dynamic programming patterns — interval DP, tree DP with rerooting, bitmask DP, digit DP, and optimization techniques like Knuth's and divide-and-conquer optimization.
·12 min read · #dsa#dynamic-programming#advanced
Competitive Programming Patterns: 15 Essential Techniques
The 15 most common competitive programming patterns — prefix sums, difference arrays, coordinate compression, meet in the middle, sqrt decomposition, sparse tables, binary lifting, and Mo's algorithm.
·12 min read · #dsa#competitive-programming#patterns
Advanced Graph Algorithms: SCCs, Flows & Bridges
Deep dive into advanced graph algorithms — Tarjan's and Kosaraju's for SCCs, bridges and articulation points, Euler paths, network flow, and 2-SAT with real-world applications.
·11 min read · #dsa#graphs#advanced
Advanced String Algorithms: Z, Rabin-Karp & Suffix Arrays
Master advanced string algorithms — Z-algorithm, Rabin-Karp rolling hash, suffix arrays, Aho-Corasick multi-pattern matching, Manacher's palindrome algorithm, and string hashing techniques.
·11 min read · #dsa#strings#advanced
Advanced Tree Algorithms: HLD, Centroid & Euler Tour
Deep dive into advanced tree algorithms — heavy-light decomposition, Euler tour technique, centroid decomposition, LCA with binary lifting, tree DP with rerooting, and virtual trees.
·11 min read · #dsa#trees#advanced