The Practice Engine

Practice
Like a Staff Engineer.

182 PROBLEMS

Dynamic Programming in Java: Demystifying the 0/1 Knapsack Pattern

Conquer dynamic programming interviews by mastering the 0/1 Knapsack pattern. Learn the transition from recursive brute force to top-down memoization, bottom-up tabulation, and space optimization.

9 MIN READ

Medium

dsajava

Pattern Blueprint: The Backtracking Master Template

Never get lost in a recursion tree again. Master the three-step Backtracking template used for combinations, permutations, and grid searches.

6 MIN READ

Medium

dsajava

Pattern Blueprint: The Monotonic Stack Template

Learn how to solve "Next Greater Element" and "Largest Area" problems in linear time using a Monotonic Stack blueprint.

6 MIN READ

Medium

dsajava

Pattern Blueprint: The Universal Sliding Window Template

Never struggle with sliding window boundaries again. Use this battle-tested Java template for all fixed and variable window problems.

6 MIN READ

Medium

dsajava

Pattern Blueprint: The Two Pointers Master Template

Learn the three distinct Two Pointer strategies: Opposite Ends, Fast & Slow, and Multiple Inputs. Perfect for array and linked list optimization.

6 MIN READ

Hard

ai-mldsa

DSA Masterclass: Dijkstra’s vs. Bellman-Ford (Shortest Path Algorithms)

6 MIN READ

Medium

dsa

Binary Search: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master Binary Search variations.

5 MIN READ

Easy

dsajava

DSA Masterclass Module 12: Binary Search Patterns

Learn how to search in logarithmic time. Master standard binary search, rotated arrays, and the powerful "Search on Answer" technique.

5 MIN READ

Hard

ai-mldsa

System Design Module 8: CAP Theorem & Consistency Models

Master the laws of distributed systems. Learn how to navigate the trade-offs between Consistency, Availability, and Partition Tolerance.

6 MIN READ

Easy

dsa

DSA Complexity: Curated Practice Problems

Test your algorithmic analysis skills with 8 hand-picked complexity challenges.

5 MIN READ

Medium

databasesdsa

System Design Module 6: Database Design (SQL vs NoSQL)

Master the most critical decision in system design. Learn the technical trade-offs between relational databases and various NoSQL models.

5 MIN READ

Medium

dsa

Dynamic Programming: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master Memoization and Tabulation.

5 MIN READ

Hard

dsajava

The Dynamic Programming Masterclass: Tabulation, Memoization, and State

Master the most feared interview topic. Learn the "Five Steps to DP", Memory Compression (O(1) space), and Staff-level intuition for state transitions.

6 MIN READ

Medium

dsa

Graphs: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master BFS, DFS, and Topological Sort.

5 MIN READ

Medium

dsajava

The Graph Mastery Blueprint: BFS, DFS, and Representation

Master the logic of Graphs. Learn how to choose between Adjacency Lists and Matrices, cycle detection algorithms, and Staff-level intuition for global-scale networks.

6 MIN READ

Medium

dsajava

DSA Masterclass Module 11: Greedy Algorithms

Learn how to solve optimization problems using the Greedy approach. Master interval scheduling, Huffman coding, and how to prove that a local optimum leads to a global one.

6 MIN READ

Medium

dsa

Greedy Algorithms: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master the Greedy approach.

5 MIN READ

Medium

dsa

Heaps: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master Priority Queues and partial sorting.

5 MIN READ

Medium

dsajava

DSA Masterclass Module 13: Heaps & Priority Queues

Learn how to manage top elements and streaming data using Heaps. Master Min-Heaps, Max-Heaps, Top K problems, and how to track the median of a data stream.

5 MIN READ

Easy

dsa

Lesson: The FAANG Interview Checklist

A step-by-step checklist to follow during every 45-minute technical interview.

7 MIN READ

Easy

dsa

DSA Masterclass Module 15: Mock Interviews & Strategy

Coding is only 20% of the interview. Learn how to communicate your thoughts, handle hints, and lead the technical conversation to a "Strong Hire" recommendation.

5 MIN READ

Medium

dsajava

Linked List Deep Dive: Memory, References, and Pointers

Go beyond the basics of Linked Lists. Master the internal memory representation, pointer manipulation, and the 'Sentinel Node' pattern for robust coding.

5 MIN READ

Medium

dsa

Linked Lists: Curated Practice Problems

A list of 10 essential LeetCode problems to master Linked List manipulation.

5 MIN READ

Medium

dsasystem-design

LLD Design Patterns: Curated Practice Problems

Test your pattern recognition skills with 10 real-world design scenarios.

6 MIN READ

Medium

dsasystem-design

LLD Masterclass: Curated Practice Problems

A hand-picked list of the top 10 LLD interview questions with pattern matches.

6 MIN READ

Easy

dsa

DSA Masterclass Module 2: The Problem Solving Mindset

Stop freezing during coding interviews. Learn a repeatable framework to decompose complex DSA problems, identify patterns, and communicate your thought process.

5 MIN READ

Medium

dsa

Recursion & Backtracking: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master decision trees and recursive logic.

5 MIN READ

Medium

dsajava

Mastering Recursion: The Three Laws and the Decision Tree

Master the art of thinking recursively. Learn the 'Three Laws', how to visualize the call stack, Tail Recursion, and Staff-level intuition for Backtracking.

5 MIN READ

Medium

dsa

Sliding Window Pattern: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master the Sliding Window pattern.

6 MIN READ

Medium

dsa

Stack & Queue: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master Stacks, Queues, and Monotonic structures.

5 MIN READ

Easy

dsajava

DSA Masterclass Module 6: Stack, Queue & Monotonic Stack

Master linear data structures with LIFO and FIFO properties. Learn how to recognize problems solvable with Stacks and Queues.

5 MIN READ

Easy

dsajava

DSA Masterclass Module 1: Time & Space Complexity

Learn how to analyze algorithms like a FAANG engineer. Master Big-O notation, time/space complexity trade-offs, and how to calculate recursion depth.

5 MIN READ

Medium

dsa

Trees: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master Tree traversals and BST properties.

5 MIN READ

Medium

dsajava

The Binary Tree Masterclass: BFS, DFS, and Structural Intuition

Master the mental models for Binary Trees. Learn the four essential traversal patterns, recursion depth analysis, and Staff-level intuition for self-balancing structures.

6 MIN READ

Hard

dsa

Tries: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master Prefix Trees and string optimization.

5 MIN READ

Hard

dsajava

DSA Masterclass Module 14: Tries & Advanced Structures

Learn how to handle string prefixes and dictionary lookups in linear time. Master Tries and discover advanced structures like Segment Trees.

5 MIN READ

Medium

dsa

Arrays & Two Pointers: Curated Practice Problems

A hand-picked list of 10 essential LeetCode problems to master the Two Pointers pattern.

5 MIN READ

Easy

dsa

Lesson: How to Explain DSA Solutions

Learn the verbal scripts to present your DSA logic confidently to FAANG interviewers.

5 MIN READ

Hard

dsajava

DSA Masterclass: The Bitmasking & XOR Blueprint

Learn how to use bitwise operators to solve subset problems and optimize state-based DP in O(1) time and O(1) space.

7 MIN READ

Medium

dsajava

Merge Intervals Pattern in Java: Conquer Overlapping Subarrays Efficiently

Master the Merge Intervals pattern in Java to solve complex overlapping subarray problems. Learn the sorting intuition, algorithm, dry runs, and time complexity analysis for FAANG interviews.

9 MIN READ

Hard

dsajava

Company Playbook: The Google 15

Master the exact problems and patterns Google interviewers use to calibrate candidates for L5 and L6 roles.

6 MIN READ

Hard

dsajava

Company Playbook: The Meta 15

Master the exact problems and patterns Meta interviewers use to evaluate speed, correctness, and optimization for E5 and E6 roles.

6 MIN READ

Medium

dsajava

3Sum - Finding Unique Triplets

Master the logic of combining sorting with two-pointer search. Learn how to solve the unique triplet problem in O(N^2) time while avoiding duplicates.

6 MIN READ

Hard

dsajava

8: Alien Dictionary (Hard)

Learn how to reconstruct the character order of an unknown language using Graph TopoSort and adjacency lists. Master dependency management at scale.

6 MIN READ

Hard

dsajava

15: Basic Calculator II (Hard)

Learn how to implement a mathematical expression evaluator with operator precedence (+, -, *, /) in O(n) time.

5 MIN READ

Easy

dsajava

Binary Search (Easy)

Master the quintessential search algorithm. Learn how to eliminate half the search space in every step to achieve logarithmic time complexity.

6 MIN READ

Easy

dsajava

Binary Tree In-order Traversal (Easy)

Master the fundamental tree traversal. Learn how to visit nodes in sorted order for BSTs and compare recursive vs. iterative implementations.

5 MIN READ

Medium

dsajava

Binary Tree Level Order Traversal

Master the logic of Breadth-First Search (BFS) on trees. Learn how to use a Queue to process nodes level-by-level, the foundation for side-view and width problems.

6 MIN READ

Hard

dsajava

29: Burst Balloons (Hard)

Learn the "Interval DP" pattern to solve optimization problems where the last choice determines the subproblem boundaries.

5 MIN READ

Medium

dsajava

Coin Change

Learn how to find the minimum number of coins to make a target amount using bottom-up DP.

6 MIN READ

Medium

dsajava

Combination Sum

Learn how to find all unique combinations that sum to a target with pruning.

6 MIN READ

Medium

dsajava

Container With Most Water (Medium)

Master the greedy two-pointer strategy. Learn why moving the shorter line is the only way to find a potentially larger area in O(N) time.

6 MIN READ

Hard

dsajava

46: Count Vowels Permutation (Hard)

Master the application of state-machine transitions converted into Dynamic Programming equations.

5 MIN READ

Medium

dsajava

Course Schedule (Topological Sort)

Master the logic of Directed Acyclic Graphs (DAG). Learn how to use Kahn’s algorithm or DFS to detect cycles in dependency systems.

6 MIN READ

Hard

dsajava

43: Cut Off Trees for Golf Event (Hard)

Master multi-stage BFS traversal on a grid to find the shortest path connecting multiple ordered points.

6 MIN READ

Medium

dsajava

Daily Temperatures (Monotonic Stack)

Master the logic of looking into the future. Learn how to use a Monotonic Stack to find the 'Next Warmer Day' in linear O(N) time.

6 MIN READ

Hard

dsajava

42: Design In-Memory File System (Hard)

Learn how to model hierarchical structures and implement commands like ls, mkdir, and read/write using an N-ary Tree design.

5 MIN READ

Hard

dsajava

39: Design Search Autocomplete System (Hard)

Learn how to design an efficient search autocomplete system using a Trie combined with caching of top historical results.

6 MIN READ

Hard

dsajava

13: Edit Distance (Hard)

Learn how to find the minimum operations to transform one word into another using a 2D DP matrix.

5 MIN READ

Hard

dsajava

24: Employee Free Time (Hard)

Learn how to find common free time slots across multiple employee schedules using a Min-Heap in O(n log k) time.

5 MIN READ

Hard

dsajava

34: Find Median from Data Stream (Hard)

1. Problem Statement......

6 MIN READ

Hard

dsajava

27: First Missing Positive (Hard)

Learn the "Index as Hash" trick to find the smallest missing positive integer in linear time with zero extra space.

5 MIN READ

Easy

dsajava

Flood Fill (Easy)

Master the grid traversal pattern. Learn how to use DFS or BFS to propagate changes across a 2D matrix, a core logic for "Number of Islands" and "Word Search".

6 MIN READ

Medium

dsajava

Group Anagrams

Master the logic of grouping items by a unique fingerprint. Learn how to transform strings into frequency keys for O(N*K) complexity.

5 MIN READ

Hard

dsajava

33: Insert Interval (Hard)

Learn how to insert and merge overlapping intervals in a sorted list in O(n) time.

5 MIN READ

Medium

dsajava

Jump Game

Learn how to determine if you can reach the end of an array using the greedy "max reach" strategy.

5 MIN READ

Medium

dsajava

Koko Eating Bananas (Search on Answer)

Learn the "Search on Answer" technique to solve complex optimization problems using binary search.

6 MIN READ

Medium

dsajava

Kth Largest Element in an Array

Learn how to find the Kth largest element using a Min-Heap in O(n log k) time.

6 MIN READ

Hard

dsajava

14: K-th Smallest in Lexicographical Order (Hard)

Master the "Denary Tree" traversal to find the K-th lexicographical number in O(log^2 N) time.

5 MIN READ

Hard

dsajava

26: Largest Rectangle in Histogram (Hard)

Learn how to find the largest rectangular area in a histogram in linear time using a Monotonic Stack.

5 MIN READ

Hard

dsajava

16: LFU Cache Design (Hard)

Learn how to design a "Least Frequently Used" cache. Master the O(1) complexity requirement using multiple Doubly Linked Lists and a frequency map.

6 MIN READ

Easy

dsajava

Linked List Cycle (Easy)

Master the Fast & Slow pointer pattern. Learn Floyd’s Cycle-Finding Algorithm to detect loops in linear data structures with O(1) space.

6 MIN READ

Hard

dsajava

22: Longest Increasing Path in a Matrix (Hard)

Learn how to find the longest path of increasing values in a 2D grid using DFS and Memoization in O(M*N) time.

5 MIN READ

Medium

dsajava

Longest Increasing Subsequence

Learn how to find the longest strictly increasing subsequence in O(n^2) and O(n log n).

6 MIN READ

Medium

dsajava

Longest Substring with K Distinct Characters

Master the variable-size sliding window pattern by finding the longest substring with K unique characters.

5 MIN READ

Hard

dsajava

11: Longest Valid Parentheses (Hard)

Learn how to find the longest substring of well-formed parentheses in O(n) time using Dynamic Programming.

5 MIN READ

Medium

dsajava

Lowest Common Ancestor of a Binary Tree

Master the logic of result propagation in recursion. Learn how to identify the "Split Point" where two nodes diverge in a tree in O(N) time.

7 MIN READ

Hard

dsajava

5: LRU Cache Design (Hard)

Master the "Least Recently Used" cache design. Learn why combining a HashMap and a Doubly Linked List is the only way to achieve O(1) for both operations.

6 MIN READ

Hard

dsajava

41: Making A Large Island (Hard)

Learn how to optimize grid problems using Union-Find and connected components to evaluate "what-if" scenarios in O(N^2) time.

6 MIN READ

Easy

dsajava

Maximum Sum Subarray of Size K

Learn how to find the maximum sum of a fixed-size contiguous subarray in O(n) time.

5 MIN READ

Hard

dsajava

25: Maximal Rectangle (Hard)

Learn how to find the largest rectangle containing only 1's in a binary matrix using a Monotonic Stack optimization.

5 MIN READ

Hard

dsajava

45: Maximize Score After N Operations (Hard)

Learn how to combine Dynamic Programming with Bitmasking to solve complex combinatorial optimization problems in O(2^N * N^2) time.

6 MIN READ

Easy

dsajava

Maximum Depth of Binary Tree

Learn how to find the height of a binary tree using recursive DFS.

5 MIN READ

Hard

dsajava

35: Maximum Profit in Job Scheduling (Hard)

Learn how to combine Dynamic Programming with Binary Search to solve complex interval scheduling optimization in O(n log n).

6 MIN READ

Hard

dsajava

2: Median of Two Sorted Arrays (Expert)

1. Problem Statement......

6 MIN READ

Easy

dsajava

Meeting Rooms (Interval Scheduling)

Learn how to find the maximum number of non-overlapping intervals using the Greedy approach.

5 MIN READ

Medium

dsajava

Merge Intervals

Master the logic of overlapping intervals. Learn how to sort and merge time-based data efficiently in O(N log N) time, a core requirement for scheduling systems.

6 MIN READ

Hard

dsajava

4: Merge K Sorted Lists (Hard)

Learn how to efficiently merge multiple sorted inputs using a Priority Queue. The foundation of External Merge Sort and distributed data merging.

5 MIN READ

Hard

dsajava

23: Minimum Window Subsequence (Hard)

Learn how to solve this complex string pattern matching problem using a combination of Sliding Window and Reverse Optimization.

6 MIN READ

Hard

dsajava

37: Minimum Number of K Consecutive Bit Flips (Hard)

Learn how to solve this complex array manipulation problem using a sliding window and parity tracking in O(N) time.

5 MIN READ

Hard

dsajava

Minimum Window Substring

Solve the hardest variation of the sliding window pattern: finding the smallest substring that contains all characters of another string.

6 MIN READ

Easy

dsajava

Move Zeroes (Easy)

Master the Read/Write pointer pattern. Learn how to shuffle array elements in-place with O(1) space, a core requirement for performance-critical systems.

6 MIN READ

Hard

dsajava

12: N-Queens (Hard)

Master the backtracking pattern to place N queens on an NxN board without any queen attacking another.

5 MIN READ

Easy

dsa

Analyze Nested Loops

Learn how to identify the difference between O(n) and O(n^2) through concrete loop examples.

5 MIN READ

Medium

dsajava

Next Greater Element I

Learn how to find the first greater element to the right for every item in an array using a Monotonic Stack.

6 MIN READ

Easy

dsajava

Number of 1 Bits (Easy)

Master the logic of Bit Manipulation. Learn Brian Kernighan’s algorithm to count set bits in constant time and understand how computers store integers.

6 MIN READ

Medium

dsajava

Number of Islands (DFS/BFS)

Master the grid traversal pattern. Learn how to use Depth-First Search (DFS) to identify and count connected components in a 2D matrix.

6 MIN READ

Hard

dsajava

38: Palindrome Pairs (Hard)

Master advanced string logic by using a Trie to find all pairs of words that form a palindrome in O(N * K^2) time.

6 MIN READ

Hard

dsajava

48: Parallel Courses III (Hard)

Combine Topological Sort with Dynamic Programming to find the critical path in a dependency graph.

6 MIN READ

Medium

dsajava

Permutations

Learn how to generate all possible arrangements of an array using the backtracking pattern.

6 MIN READ

Hard

dsajava

49: Prefix and Suffix Search (Hard)

Learn how to design a specialized Trie that handles dual-ended string matching in O(L) time.

6 MIN READ

Hard

dsajava

44: Race Car (Hard)

Learn how to model a state-space search problem using BFS and DP to find the shortest sequence of instructions to reach a target.

6 MIN READ

Easy

dsajava

Range Sum Query (Easy)

Master the Prefix Sum pattern. Learn how to transform O(N) range queries into O(1) constant time by pre-calculating the cumulative totals of an array.

6 MIN READ

Easy

dsa

Analyze Recursive Depth

Learn how to calculate the space complexity of recursive functions using the recursion stack.

5 MIN READ

Hard

dsajava

31: Regular Expression Matching (Hard)

1. Problem Statement......

5 MIN READ

Easy

dsajava

Remove Duplicates from Sorted Array (In-Place)

Master the in-place array modification pattern. Learn how to use a 'Read' and 'Write' pointer to eliminate duplicates in O(N) time with O(1) space.

5 MIN READ

Hard

dsajava

7: Reverse Nodes in k-Group (Hard)

The ultimate Linked List challenge. Learn how to reverse segments of a list while maintaining referential integrity in O(N) time and O(1) space.

5 MIN READ

Easy

dsajava

Reverse a Linked List

Learn how to reverse a singly linked list in-place using pointer manipulation.

5 MIN READ

Medium

dsajava

Search in Rotated Sorted Array

Master the logic of Binary Search on shifted data. Learn how to identify the sorted half of a rotated array to achieve O(log N) search time.

6 MIN READ

Hard

dsajava

36: Serialize and Deserialize BST (Hard)

Learn how to leverage the properties of a Binary Search Tree to design an ultra-compact serialization algorithm without null markers.

5 MIN READ

Hard

dsajava

21: Serialize and Deserialize Binary Tree (Hard)

Learn how to design a compact string representation for a binary tree and reconstruct it in O(n) time.

5 MIN READ

Hard

dsajava

50: Sliding Puzzle (Hard)

Master state-space exploration by converting a 2D matrix puzzle into a 1D string and solving it with Breadth-First Search.

6 MIN READ

Hard

dsajava

6: Sliding Window Maximum (Hard)

Learn how to find the maximum in every sliding window of size K in O(n) time using a Monotonic Deque. Master the concept of "Useless Candidates" in algorithms.

6 MIN READ

Hard

dsajava

30: Smallest Range Covering Elements from K Lists (Hard)

Learn how to find the narrowest range that contains at least one number from each of K sorted lists using a Min-Heap.

5 MIN READ

Hard

dsajava

10: Sudoku Solver (Hard)

Master the depth-first search approach to solve a 9x9 Sudoku puzzle using recursive backtracking.

6 MIN READ

Hard

dsajava

40: Swim in Rising Water (Hard)

Master the application of Dijkstra's algorithm and Min-Heaps on a 2D grid to find the path of least maximum resistance.

6 MIN READ

Hard

dsajava

1: Trapping Rain Water (Hard)

The quintessential FAANG problem. Learn the 3-pass DP approach and the optimized two-pointer O(1) space solution with detailed dry runs.

6 MIN READ

Hard

dsajava

9: Binary Tree Maximum Path Sum (Hard)

Learn how to find the highest value path in a tree that can start and end at any node. Master global state management in recursion for Google interviews.

5 MIN READ

Easy

dsajava

Two Sum II: Input Array Is Sorted (Two Pointers)

Master the optimal two-pointer approach to find a pair that sums to a target in a sorted array. Learn the "Squeeze" intuition and interview scripts.

6 MIN READ

Easy

dsajava

Valid Anagram (Easy)

Master the frequency mapping pattern to determine if two strings are anagrams. Learn why an array is 10x faster than a HashMap in Java.

5 MIN READ

Hard

dsajava

47: Valid Arrangement of Pairs (Hard)

Learn how to identify and construct an Eulerian Path in a directed graph to solve advanced sequencing problems.

6 MIN READ

Easy

dsajava

Valid Palindrome (Easy)

Master the two-pointer approach to string validation. Learn how to handle alphanumeric filtering and case-insensitivity in O(N) time with O(1) space.

6 MIN READ

Easy

dsajava

Valid Parentheses

Learn how to use a stack to validate nested structures like brackets and parentheses in O(n) time.

6 MIN READ

Medium

dsajava

Validate Binary Search Tree

Learn how to correctly validate BST properties using range boundaries in O(n).

6 MIN READ

Hard

dsajava

32: Word Break II (Hard)

Master the combination of Dynamic Programming and Backtracking to generate all possible sentence constructions.

5 MIN READ

Hard

dsajava

17: Word Ladder (Hard)

Learn how to find the shortest transformation sequence between two words using Breadth-First Search on a string graph.

5 MIN READ

Hard

dsajava

28: Word Ladder II (Hard)

Learn how to reconstruct all shortest transformation sequences between two words using BFS and Backtracking.

5 MIN READ

Hard

dsajava

3: Word Search II (Hard)

Learn the master-tier optimization of using a Trie to prune recursive DFS branches on a 2D board. Master multi-word searching at global scale.

5 MIN READ

Medium

dsajava

The Sliding Window Pattern: Eliminating Redundant Calculations

Master the logic of Sliding Windows. Learn how to convert O(N^2) array problems into O(N) linear time using fixed and dynamic window strategies for MANG interviews.

5 MIN READ

Easy

dsajava

Tree Traversals in Java: Mastering BFS and DFS for Coding Interviews

Learn the essential tree traversal patterns in Java. Master Breadth-First Search (BFS) and Depth-First Search (DFS) with iterative and recursive templates, dry runs, and complexity analysis.

8 MIN READ

Hard

dsajava

Trie (Prefix Tree) in Java: The Ultimate Data Structure for String Problems

Master the Trie (Prefix Tree) data structure in Java. Learn its intuition, implementation, dry runs, and time complexity analysis for autocomplete, spell checkers, and FAANG interviews.

8 MIN READ

Medium

dsajava

The Two Pointers Pattern: Mastering Linear Array Optimizations

Master the four distinct variations of the Two Pointers pattern. Learn the mental models, complexity analysis, and senior-level interview follow-ups for MANG.

6 MIN READ

Medium

dsajava

Centroid Decomposition in Java: Solving Tree Path Problems

Master Centroid Decomposition in Java. Learn how to recursively divide a tree into subtrees to solve complex path-related queries in O(N log N) time.

7 MIN READ

Hard

dsajava

Heavy-Light Decomposition in Java: Optimizing Tree Queries

Master Heavy-Light Decomposition (HLD) in Java. Learn how to decompose a tree into paths to perform efficient path queries and updates in O(log² N) time.

5 MIN READ

Hard

dsajava

Link-Cut Trees in Java: Dynamic Tree Connectivity

Master Link-Cut Trees (LCT) in Java. Learn how to maintain a forest of trees and perform path queries and connectivity updates in O(log N) time using splay trees.

6 MIN READ

Medium

dsajava

Suffix Automaton in Java: The Ultimate String Data Structure

Master Suffix Automaton (SAM) in Java. Learn how to build this powerful structure in linear time to solve complex string problems like substring counting and pattern matching.

5 MIN READ

Medium

dsajava

AVL Trees: Self-Balancing Binary Search Trees

Master AVL trees, a self-balancing binary search tree. Learn how they maintain O(log N) operations through rotations.

6 MIN READ

Easy

awsdata-engineering

The 'Small Files' Problem in Data Lakes: Why Your Kafka Sink is Slow

Why does writing data from Kafka to S3 slow down over time? Learn about the 'Small Files' problem and how to implement a compaction strategy for your Data Lake.

7 MIN READ

Hard

dsajava

Kosaraju's Algorithm for Strongly Connected Components

Master Kosaraju's algorithm for finding Strongly Connected Components in a Directed Graph using Java. Learn the two-pass DFS approach.

7 MIN READ

Medium

dsajava

Manacher's Algorithm in Java: Linear Time Palindrome Search

Master Manacher's algorithm for finding the longest palindromic substring in O(N) time. Learn how to use symmetry and pre-processing to optimize palindrome detection.

7 MIN READ

Hard

dsajava

Mo's Algorithm: Offline Range Queries

Master Mo's Algorithm, a powerful technique for solving offline range query problems in O((N+Q) * sqrt(N)) time.

6 MIN READ

Medium

dsajava

Red-Black Trees in Java: The Engine Behind TreeMap and HashMap

Master Red-Black Trees in Java. Learn the five properties that maintain balance, how to handle rotations and recoloring, and why this structure is preferred for write-heavy applications.

5 MIN READ

Medium

dsajava

Segment Tree Data Structure: Efficient Range Queries

Master Segment Tree for efficient range queries and updates. Learn implementation in Java.

6 MIN READ

Medium

dsajava

Skip Lists in Java: The Probabilistic Alternative to Balanced Trees

Master Skip Lists in Java. Learn how this probabilistic data structure achieves O(log N) search, insertion, and deletion without the complexity of rotations or balancing logic.

5 MIN READ

Hard

dsasystem-design

System Design: Solving the Top K Problem (Heavy Hitters)

How does YouTube track trending videos or Twitter find trending hashtags in real-time? Learn about the Top K problem, Count-Min Sketch, and heavy hitters at scale.

7 MIN READ

Medium

dsajava

Tarjan's Algorithm in Java: Finding Strongly Connected Components

Master Tarjan's algorithm for finding Strongly Connected Components (SCCs) in a directed graph. Learn how to use a single DFS pass with low-link values to identify cycles and connectivity.

7 MIN READ

Medium

dsajava

Trie (Prefix Tree) Data Structure - Java Implementation and Use Cases

A comprehensive guide to the Trie (Prefix Tree) data structure in Java, including implementation details and real-world applications.

6 MIN READ

Easy

dsajava

A* Search Algorithm in Java: Heuristic Pathfinding

Master the A* search algorithm in Java. Learn how it combines Dijkstra's logic with heuristics to find the shortest path significantly faster in maps and grids.

7 MIN READ

Hard

dsajava

B-Trees and B+ Trees in Java: The Engines of Modern Databases

Understand the architecture of B-Trees and B+ Trees. Learn why these self-balancing trees are the standard for file systems and database indexing, and how they differ from Binary Search Trees.

7 MIN READ

Medium

dsajava

Backtracking Pattern in Java: Permutations and Combinations

Master the Backtracking algorithm in Java for generating permutations and combinations. Learn its intuition, recursive implementation, dry runs, and complexity analysis for solving combinatorial problems.

13 MIN READ

Medium

ai-mldsa

Bellman-Ford Algorithm in Java: Shortest Paths with Negative Weights

Master Bellman-Ford Algorithm in Java for finding shortest paths in weighted graphs, including those with negative edge weights. Learn its intuition, implementation, dry runs, and how to detect negative cycles.

12 MIN READ

Medium

dsajava

Bloom Filters in Java: Probabilistic Data Structures

Master Bloom Filters in Java. Learn how this memory-efficient probabilistic data structure checks for set membership with zero false negatives and controllable false positives.

7 MIN READ

Medium

dsajava

Boyer-Moore Voting Algorithm in Java: Finding the Majority Element

Learn the Boyer-Moore Voting Algorithm in Java. Discover how to find the majority element in an array in linear time and constant space, a common and elegant interview favorite.

7 MIN READ

Medium

dsajava

Dijkstra's Algorithm in Java: Finding the Shortest Path

Master Dijkstra's shortest path algorithm in Java. Learn the greedy logic, how to use PriorityQueue for efficiency, and how to solve common weighted graph interview problems.

7 MIN READ

Medium

dsajava

Fenwick Trees (Binary Indexed Trees) in Java

Learn how to implement a Fenwick Tree in Java. Discover the power of Binary Indexed Trees (BIT) for efficient prefix sum queries and point updates in logarithmic time.

7 MIN READ

Medium

dsajava

Floyd-Warshall Algorithm in Java: All-Pairs Shortest Paths

Master the Floyd-Warshall algorithm in Java. Learn how to find the shortest distances between all pairs of vertices in a weighted graph, including those with negative edge weights.

7 MIN READ

Hard

dsajava

Huffman Coding in Java: Lossless Data Compression

Master the Huffman Coding algorithm in Java. Learn how to use a Greedy approach and a PriorityQueue to build an optimal prefix-free code for data compression.

7 MIN READ

Medium

dsajava

Kadane's Algorithm in Java: Maximum Sum Subarray

Master Kadane's Algorithm in Java. Learn how to find the maximum sum of a contiguous subarray in linear time using dynamic programming principles.

7 MIN READ

Easy

dsajava

Kruskal's Algorithm in Java: Finding the Minimum Spanning Tree

Learn how to implement Kruskal's algorithm in Java. Understand how it uses the Greedy approach and Union-Find data structure to find the Minimum Spanning Tree (MST) of a graph.

7 MIN READ

Easy

dsajava

Longest Common Subsequence (LCS) in Java: Dynamic Programming Guide

Master the Longest Common Subsequence (LCS) problem in Java. Learn the recursive approach with memoization and the optimized bottom-up tabulation method.

7 MIN READ

Hard

dsajava

Lowest Common Ancestor (LCA) in Java: Binary Trees and DAGs

Master the concept of Lowest Common Ancestor (LCA) in Java for binary trees and Directed Acyclic Graphs (DAGs). Learn various approaches, their implementations, dry runs, and complexity analysis.

12 MIN READ

Medium

dsajava

LRU Cache Implementation in Java: $O(1)$ Strategy

Master the Least Recently Used (LRU) cache implementation in Java. Learn how to combine a HashMap with a Doubly Linked List to achieve constant time complexity for both get and put operations.

7 MIN READ

Medium

dsajava

Matrix Traversal in Java: Spiral, Diagonal, and Flood Fill

Master various matrix traversal techniques in Java, including spiral order, diagonal traversal, and flood fill. Learn their intuition, implementation, dry runs, and complexity analysis for solving common grid-based problems.

13 MIN READ

Hard

ai-mldsa

N-Queens Problem in Java: Solving Constraints with Backtracking

Master the N-Queens problem in Java using backtracking. Learn its intuition, recursive implementation, dry runs, and complexity analysis for solving this classic combinatorial puzzle.

12 MIN READ

Medium

dsajava

Prim's Algorithm in Java: Minimum Spanning Tree via Greedy Growth

Master Prim's algorithm in Java. Learn how to use a PriorityQueue to build a Minimum Spanning Tree (MST) by growing it one vertex at a time from a starting node.

5 MIN READ

Medium

dsajava

Rabin-Karp Algorithm in Java: Efficient String Searching with Hashing

Master the Rabin-Karp algorithm in Java. Learn how to use rolling hashes to find a pattern in a text in average linear time, and how to handle hash collisions effectively.

5 MIN READ

Medium

ai-mldsa

Sudoku Solver in Java: Efficient Backtracking and Pruning

Learn to solve Sudoku puzzles efficiently using backtracking in Java. This article covers the intuition, recursive implementation, dry runs, and complexity analysis, including strategies for effective pruning.

11 MIN READ

Hard

dsajava

Suffix Arrays and Suffix Trees in Java: Advanced String Structures

Master Suffix Arrays and Suffix Trees in Java. Learn how these advanced structures enable O(m log n) substring searching and solve complex string problems in linear time.

7 MIN READ

Hard

dsajava

Z-Algorithm in Java: Linear Time String Matching

Master the Z-Algorithm in Java. Learn how to find all occurrences of a pattern in a text in linear time using the Z-array, a powerful alternative to KMP.

7 MIN READ

Medium

dsajava

BFS (Breadth First Search) in Java: Level-Order and Shortest Path

Master Breadth First Search (BFS) in Java for traversing trees and graphs. Learn its intuition, iterative implementation, dry runs, and complexity analysis for level-order traversal and shortest path problems.

11 MIN READ

Easy

dsajava

Big-O Notation in Java: Time and Space Complexity for Interview Problem Solving

A practical Java-first guide to Big-O notation for interviews. Learn how to analyze loops, recursion, collections, amortized complexity, and common mistakes with clear code examples.

11 MIN READ

Easy

dsajava

Binary Search Pattern in Java: Efficiently Searching Sorted Data

Master the Binary Search pattern in Java for efficiently searching sorted arrays. Learn its intuition, algorithm, dry runs, and variations like searching in rotated arrays and on answers.

12 MIN READ

Medium

dsajava

DFS (Depth First Search) in Java: Tree and Graph Traversals

Master Depth First Search (DFS) in Java for traversing trees and graphs. Learn its intuition, iterative and recursive implementations, dry runs, and complexity analysis for various applications.

12 MIN READ

Medium

dsajava

Dutch National Flag Pattern in Java: Efficient Three-Way Partitioning

Master the Dutch National Flag (DNF) pattern in Java for efficient in-place three-way partitioning of arrays. Learn its intuition, algorithm, dry runs, and complexity analysis for optimal solutions.

9 MIN READ

Medium

dsajava

Fast & Slow Pointers in Java: Detecting Cycles and Finding Middle Elements

Master the Fast & Slow Pointers pattern in Java for efficient cycle detection, finding middle elements, and other linked list problems. Learn its intuition, algorithm, dry runs, and complexity analysis.

12 MIN READ

Medium

dsajava

In-place Reversal of a Linked List in Java: Efficient Memory Management

Master the in-place reversal of a linked list in Java. Learn the iterative and recursive approaches, their intuition, dry runs, and complexity analysis for optimal memory usage.

9 MIN READ

Medium

dsajava

Monotonic Queue Pattern in Java: Efficiently Solving Sliding Window Maximum

Master the Monotonic Queue pattern in Java for efficiently solving sliding window maximum/minimum problems. Learn its intuition, algorithm, dry runs, and complexity analysis.

12 MIN READ

Medium

dsajava

Monotonic Stack Pattern in Java: Efficiently Finding Next Greater/Smaller Elements

Master the Monotonic Stack pattern in Java for efficiently solving problems like Next Greater Element, Next Smaller Element, and related array/list challenges. Learn its intuition, algorithm, dry runs, and complexity analysis.

11 MIN READ

Medium

dsajava

Prefix Sum Pattern in Java: Efficiently Calculate Range Sums and Subarray Properties

Master the Prefix Sum pattern in Java to optimize solutions for problems involving range sums, subarray properties, and contiguous segments. Learn precomputation, dry runs, and complexity analysis.

9 MIN READ

Medium

dsajava

Sorting Algorithms in Java: QuickSort, MergeSort, and HeapSort Explained

Master fundamental sorting algorithms in Java: QuickSort, MergeSort, and HeapSort. Learn their intuition, implementation, complexity analysis, and when to use each for optimal performance.

12 MIN READ

Medium

dsajava

Topological Sort in Java: Handling Dependencies with Kahn's Algorithm

Master Topological Sort in Java using Kahn's Algorithm for ordering tasks with dependencies. Learn its intuition, implementation, dry runs, and complexity analysis for various scheduling and dependency problems.

10 MIN READ

Medium

dsajava

Union Find (DSU) in Java: Connectivity and Cycle Detection

Master the Union Find (Disjoint Set Union) data structure in Java for efficiently managing disjoint sets, checking connectivity, and detecting cycles in undirected graphs. Learn its intuition, implementation, dry runs, and complexity analysis.

10 MIN READ

Practice Like a Staff Engineer.

Dynamic Programming in Java: Demystifying the 0/1 Knapsack Pattern

Pattern Blueprint: The Backtracking Master Template

Pattern Blueprint: The Monotonic Stack Template

Pattern Blueprint: The Universal Sliding Window Template

Pattern Blueprint: The Two Pointers Master Template

DSA Masterclass: Dijkstra’s vs. Bellman-Ford (Shortest Path Algorithms)

Binary Search: Curated Practice Problems

DSA Masterclass Module 12: Binary Search Patterns

System Design Module 8: CAP Theorem & Consistency Models

DSA Complexity: Curated Practice Problems

System Design Module 6: Database Design (SQL vs NoSQL)

Dynamic Programming: Curated Practice Problems

The Dynamic Programming Masterclass: Tabulation, Memoization, and State

Graphs: Curated Practice Problems

The Graph Mastery Blueprint: BFS, DFS, and Representation

DSA Masterclass Module 11: Greedy Algorithms

Greedy Algorithms: Curated Practice Problems

Heaps: Curated Practice Problems

DSA Masterclass Module 13: Heaps & Priority Queues

Lesson: The FAANG Interview Checklist

DSA Masterclass Module 15: Mock Interviews & Strategy

Linked List Deep Dive: Memory, References, and Pointers

Linked Lists: Curated Practice Problems

LLD Design Patterns: Curated Practice Problems

LLD Masterclass: Curated Practice Problems

DSA Masterclass Module 2: The Problem Solving Mindset

Recursion & Backtracking: Curated Practice Problems

Mastering Recursion: The Three Laws and the Decision Tree

Sliding Window Pattern: Curated Practice Problems

Stack & Queue: Curated Practice Problems

DSA Masterclass Module 6: Stack, Queue & Monotonic Stack

DSA Masterclass Module 1: Time & Space Complexity

Trees: Curated Practice Problems

The Binary Tree Masterclass: BFS, DFS, and Structural Intuition

Tries: Curated Practice Problems

DSA Masterclass Module 14: Tries & Advanced Structures

Arrays & Two Pointers: Curated Practice Problems

Lesson: How to Explain DSA Solutions

DSA Masterclass: The Bitmasking & XOR Blueprint

Merge Intervals Pattern in Java: Conquer Overlapping Subarrays Efficiently

Company Playbook: The Google 15

Company Playbook: The Meta 15

3Sum - Finding Unique Triplets

8: Alien Dictionary (Hard)

15: Basic Calculator II (Hard)

Binary Search (Easy)

Binary Tree In-order Traversal (Easy)

Binary Tree Level Order Traversal

29: Burst Balloons (Hard)

Coin Change

Combination Sum

Container With Most Water (Medium)

46: Count Vowels Permutation (Hard)

Course Schedule (Topological Sort)

43: Cut Off Trees for Golf Event (Hard)

Daily Temperatures (Monotonic Stack)

42: Design In-Memory File System (Hard)

39: Design Search Autocomplete System (Hard)

13: Edit Distance (Hard)

24: Employee Free Time (Hard)

34: Find Median from Data Stream (Hard)

27: First Missing Positive (Hard)

Flood Fill (Easy)

Group Anagrams

33: Insert Interval (Hard)

Jump Game

Koko Eating Bananas (Search on Answer)

Kth Largest Element in an Array

14: K-th Smallest in Lexicographical Order (Hard)

26: Largest Rectangle in Histogram (Hard)

16: LFU Cache Design (Hard)

Linked List Cycle (Easy)

22: Longest Increasing Path in a Matrix (Hard)

Longest Increasing Subsequence

Longest Substring with K Distinct Characters

11: Longest Valid Parentheses (Hard)

Lowest Common Ancestor of a Binary Tree

5: LRU Cache Design (Hard)

41: Making A Large Island (Hard)

Practice
Like a Staff Engineer.