Interview Preparation
Master coding interviews with LeetCode patterns, system design frameworks, and mock interview practice.
LeetCode Patterns
Mastering the Two-Pointer Technique for LeetCode Interviews
A comprehensive guide to the two-pointer pattern used in dozens of LeetCode problems, with detailed examples and complexity analysis.
Dive deeper →Solving Two Sum II on a Sorted Array
Learn how to solve Two Sum II using the two-pointer technique on a sorted array for optimal O(n) time complexity.
View details →Container With Most Water: Optimal Two-Pointer Strategy
Master the two-pointer approach to solve the Container With Most Water problem in linear time.
Get started →Three Sum Problem: Complete Walkthrough
A detailed guide to solving the Three Sum problem using sorting and two pointers to find all unique triplets.
Get started →Trapping Rain Water Using Two Pointers
Solve the classic Trapping Rain Water problem using the optimal two-pointer approach with O(1) space.
Explore guide →Remove Duplicates from Sorted Array II
Handle the variation where each element may appear at most twice using the two-pointer technique.
Dive deeper →Four Sum Problem: Multi-Pointer Solution
Extend the two-pointer technique to solve the Four Sum problem by reducing it to multiple Two Sum subproblems.
See full guide →Partition Labels Using Two Pointers and Greedy
Learn how to partition a string into the maximum number of parts so that each letter appears in at most one part.
Explore guide →Longest Substring Without Repeating Characters
Use the sliding window technique with a hash set to find the longest substring without repeating characters.
See full guide →Minimum Window Substring: Sliding Window Mastery
A comprehensive guide to solving Minimum Window Substring using the expand-and-contract sliding window pattern.
Get started →Maximum Sum Subarray of Size K
Understand the fixed-size sliding window pattern by finding the maximum sum subarray of a given size.
Learn more →Longest Repeating Character Replacement
Solve the Longest Repeating Character Replacement problem using a dynamic sliding window approach.
See full guide →Permutation in String: Sliding Window with Frequency Map
Detect if one string contains a permutation of another using a sliding window with character frequency counting.
Get started →Sliding Window Maximum Using a Deque
Use a monotonic deque to efficiently find the maximum value in every sliding window of size k.
Dive deeper →Fruit Into Baskets: Variable Sliding Window
Apply the variable-size sliding window to solve the Fruit Into Baskets problem in linear time.
See full guide →Binary Search in a Rotated Sorted Array
Learn how to adapt binary search for rotated sorted arrays to find a target element in O(log n) time.
See full guide →Find Minimum in Rotated Sorted Array
Apply binary search to find the minimum element in a rotated sorted array with and without duplicates.
Get started →Search a 2D Matrix Using Binary Search
Treat a sorted 2D matrix as a flattened sorted array and apply binary search to find target elements.
See full guide →Koko Eating Bananas: Binary Search on Answer
Use binary search on the answer space to determine the minimum eating speed for Koko to finish all bananas.
View details →Median of Two Sorted Arrays: Advanced Binary Search
Solve the classic hard problem of finding the median of two sorted arrays in O(log(min(m,n))) time.
View details →Split Array Largest Sum Using Binary Search
Apply binary search on the answer to minimize the largest sum when splitting an array into k subarrays.
View details →First Bad Version: Classic Binary Search Application
Solve the First Bad Version problem using binary search to minimize the number of API calls.
Continue reading →Number of Islands: BFS and DFS Solutions
Learn two approaches to counting connected components in a grid using both BFS and DFS traversals.
Continue reading →Word Ladder: BFS for Shortest Transformation
Use BFS to find the shortest transformation sequence from a begin word to an end word in a dictionary.
Get started →Course Schedule: Cycle Detection with DFS
Determine if all courses can be completed by detecting cycles in a directed graph using DFS.
Get started →Pacific Atlantic Water Flow: Multi-Source DFS
Solve the Pacific Atlantic Water Flow problem by running DFS from ocean borders inward.
Learn more →Clone Graph: Deep Copy with BFS or DFS
Create a deep copy of a connected undirected graph using either BFS or DFS with a visited hash map.
View details →Surrounded Regions: Border BFS Approach
Flip surrounded regions by first identifying border-connected cells using BFS then flipping the rest.
Get started →Binary Tree Level Order Traversal with BFS
Use BFS with a queue to traverse a binary tree level by level and collect nodes at each depth.
Learn more →Rotting Oranges: Multi-Source BFS
Apply multi-source BFS to simulate the spread of rot and determine the minimum time for all oranges to rot.
Explore guide →Solving the Maximum Subarray Problem with Kadane Algorithm
Master Kadane algorithm to find the maximum sum contiguous subarray in O(n) time.
See full guide →Coin Change: Complete DP Breakdown
Solve the Coin Change problem using both top-down memoization and bottom-up tabulation approaches.
See full guide →Longest Palindromic Substring: DP and Expand Around Center
Find the longest palindromic substring using dynamic programming and the expand-around-center technique.
Explore guide →House Robber Series: DP State Transitions
Solve House Robber I, II, and III to understand linear, circular, and tree DP patterns.
Get started →Climbing Stairs: Introduction to Dynamic Programming
Use the Climbing Stairs problem as a gentle introduction to dynamic programming concepts and memoization.
Continue reading →Word Break: DP with String Segmentation
Determine if a string can be segmented into dictionary words using dynamic programming.
Explore guide →Edit Distance: Classic DP on Two Strings
Compute the minimum edit distance between two strings using a 2D DP table with insert, delete, and replace operations.
Explore guide →Unique Paths: Grid DP Fundamentals
Count all unique paths in a grid from top-left to bottom-right using dynamic programming.
View details →Longest Increasing Subsequence: DP and Binary Search
Solve LIS using O(n^2) DP and then optimize to O(n log n) with patience sorting and binary search.
See full guide →Decode Ways: String DP Problem
Count the number of ways to decode a numeric string into letters using dynamic programming.
Get started →Jump Game: Greedy Reachability Check
Determine if you can reach the last index using a greedy approach that tracks the farthest reachable position.
Explore guide →Jump Game II: Minimum Number of Jumps
Find the minimum number of jumps to reach the end of an array using a greedy BFS-like approach.
Learn more →Task Scheduler: Greedy with Cooldown
Schedule tasks with cooldown constraints to minimize total intervals using a greedy frequency-based approach.
Get started →Gas Station: Circular Route Greedy Solution
Find the starting gas station for a circular route using a single-pass greedy algorithm.
Explore guide →Meeting Rooms II: Minimum Conference Rooms
Calculate the minimum number of conference rooms needed using interval sorting and a min-heap.
Explore guide →Non-Overlapping Intervals: Greedy Interval Scheduling
Remove the minimum number of intervals to make the rest non-overlapping using greedy interval scheduling.
See full guide →Candy Distribution: Two-Pass Greedy
Distribute minimum candies to children in a line such that higher-rated children get more using two greedy passes.
Dive deeper →Subsets: Backtracking to Generate All Subsets
Generate all possible subsets of an array using the backtracking pattern with include-or-exclude decisions.
Get started →Permutations: Complete Backtracking Guide
Generate all permutations of an array using backtracking with swapping and visited-set approaches.
See full guide →N-Queens: Classic Backtracking Problem
Place N queens on an N x N chessboard so no two queens attack each other using backtracking.
Learn more →Combination Sum: Backtracking with Reuse
Find all combinations that sum to a target where elements can be reused using backtracking.
Get started →Word Search in a Grid: DFS Backtracking
Search for a word in a 2D grid by exploring all directions with DFS backtracking.
Get started →Palindrome Partitioning: Backtracking Approach
Partition a string into all possible palindrome substrings using backtracking with palindrome checking.
View details →Sudoku Solver: Constraint-Based Backtracking
Solve a Sudoku puzzle using backtracking with row, column, and box constraint tracking.
Dive deeper →Union-Find for Connected Components
Use Union-Find with path compression and union by rank to efficiently count connected components in a graph.
Learn more →Redundant Connection: Union-Find Cycle Detection
Find the redundant edge in a graph that forms a cycle using Union-Find.
Learn more →Accounts Merge Using Union-Find
Merge accounts with common emails using Union-Find to group connected email addresses.
View details →Number of Provinces: Union-Find Solution
Count the number of connected provinces in an adjacency matrix using Union-Find.
Get started →Earliest Moment When Everyone Becomes Friends
Find the earliest timestamp when all people are connected using sorted events and Union-Find.
See full guide →Implement Trie (Prefix Tree) from Scratch
Build a trie data structure supporting insert, search, and startsWith operations for string processing.
View details →Word Search II: Trie Plus Backtracking
Find all words from a dictionary in a 2D board using a trie for efficient prefix matching combined with backtracking.
Explore guide →Design Search Autocomplete System with Trie
Build a search autocomplete system using a trie with frequency-based ranking of suggestions.
See full guide →Longest Word in Dictionary Using Trie
Find the longest word in a dictionary where every prefix is also a word using trie construction.
Dive deeper →Replace Words: Trie-Based Root Matching
Replace words in a sentence with their shortest root using a trie for efficient prefix lookup.
Learn more →Range Sum Query with Segment Tree
Build a segment tree to answer range sum queries and handle point updates in O(log n) time.
Continue reading →Count of Smaller Numbers After Self
Count elements smaller than each element to its right using a segment tree or modified merge sort.
Learn more →Range Minimum Query: Segment Tree Implementation
Implement a segment tree for range minimum queries with lazy propagation for range updates.
Learn more →My Calendar: Segment Tree for Interval Booking
Use a segment tree to efficiently manage calendar bookings and detect double-booking conflicts.
Get started →Course Schedule II: Topological Ordering
Find the order to take courses given prerequisites using Kahn algorithm for topological sorting.
Learn more →Alien Dictionary: Topological Sort on Characters
Derive the character ordering of an alien language from sorted words using topological sort.
Get started →Sequence Reconstruction: Unique Topological Order
Determine if a sequence can be uniquely reconstructed from subsequences using topological sort.
Dive deeper →Parallel Courses: Shortest Time with Topological Sort
Find the minimum number of semesters to complete all courses using topological sort with level tracking.
Dive deeper →Top K Frequent Elements Using a Heap
Find the k most frequent elements in an array using a min-heap of size k for optimal performance.
See full guide →Merge K Sorted Lists: Min-Heap Approach
Merge k sorted linked lists into one sorted list using a min-heap to always pick the smallest element.
View details →Find Median from Data Stream: Two Heaps
Maintain a running median using a max-heap for the lower half and a min-heap for the upper half.
Explore guide →Kth Largest Element in an Array
Find the kth largest element using a min-heap of size k or the Quickselect algorithm.
Get started →Reorganize String: Greedy with Max-Heap
Rearrange a string so no two adjacent characters are the same using a max-heap by frequency.
Explore guide →K Closest Points to Origin Using a Heap
Find k closest points to the origin using a max-heap to maintain the k smallest distances.
Explore guide →Ugly Number II: Heap-Based Generation
Generate the nth ugly number using a min-heap to always produce the next smallest ugly number.
View details →Valid Parentheses: Stack Fundamentals
Validate matching brackets in a string using a stack to track opening brackets.
View details →Daily Temperatures: Monotonic Stack Approach
Find the number of days until a warmer temperature using a monotonic decreasing stack.
Get started →Next Greater Element Using Monotonic Stack
Find the next greater element for each element in an array using a monotonic stack in O(n) time.
Dive deeper →Largest Rectangle in Histogram: Stack Solution
Find the largest rectangular area in a histogram using a monotonic stack to track bar boundaries.
Explore guide →Min Stack: Design a Stack with O(1) Minimum
Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
Explore guide →Evaluate Reverse Polish Notation with a Stack
Evaluate arithmetic expressions in reverse Polish notation using a stack for operand management.
Continue reading →Asteroid Collision: Stack-Based Simulation
Simulate asteroid collisions using a stack to determine which asteroids survive.
Learn more →Single Number: XOR Bit Manipulation
Find the single non-duplicate number in an array where every other number appears twice using XOR.
Learn more →Counting Bits: DP with Bitwise Operations
Count the number of 1-bits for every number from 0 to n using dynamic programming and bit tricks.
View details →Power of Two: Bitwise Verification
Check if a number is a power of two using the elegant n & (n-1) bit manipulation trick.
Dive deeper →Reverse Bits: Bit-by-Bit Reversal
Reverse the bits of a 32-bit unsigned integer using bit shifting and masking operations.
Learn more →Hamming Distance: XOR and Bit Counting
Calculate the Hamming distance between two integers using XOR followed by counting set bits.
Get started →Missing Number: XOR and Math Solutions
Find the missing number in a sequence using both the XOR approach and the sum formula approach.
Continue reading →Bitwise AND of Numbers Range
Compute the bitwise AND of all numbers in a range by finding the common prefix of the range boundaries.
View details →Group Anagrams: String Sorting and Hashing
Group anagrams together using sorted string keys or character frequency arrays as hash map keys.
Learn more →Longest Common Prefix: Multiple Approaches
Find the longest common prefix among an array of strings using vertical scanning or trie-based approaches.
See full guide →String to Integer (atoi): Edge Case Handling
Implement atoi to convert a string to an integer handling whitespace, signs, overflow, and invalid characters.
Continue reading →ZigZag Conversion: String Pattern Simulation
Convert a string to zigzag pattern on a given number of rows and read it line by line.
Continue reading →Multiply Strings: Large Number Multiplication
Multiply two numbers represented as strings without using built-in big integer libraries.
Learn more →Valid Palindrome: Two-Pointer String Check
Check if a string is a palindrome considering only alphanumeric characters using two pointers.
Continue reading →Implement strStr: KMP Pattern Matching
Implement string matching using the KMP algorithm with failure function for O(n+m) pattern search.
View details →LRU Cache: Design and Implementation
Design a Least Recently Used cache using a hash map and doubly linked list for O(1) operations.
See full guide →Serialize and Deserialize Binary Tree
Convert a binary tree to a string representation and back using BFS or DFS traversal strategies.
See full guide →Best Time to Buy and Sell Stock: All Variations
Solve all variations of the stock trading problem from single transaction to unlimited transactions with cooldown.
Learn more →Product of Array Except Self Without Division
Compute the product of all elements except the current one without using division in O(n) time.
Explore guide →Merge Intervals: Sorting and Sweeping
Merge overlapping intervals by sorting by start time and iterating with a merge condition.
Explore guide →Rotate Image: In-Place Matrix Rotation
Rotate an n x n matrix 90 degrees clockwise in-place using transpose and reverse operations.
Get started →Spiral Matrix: Layer-by-Layer Traversal
Traverse a matrix in spiral order by processing each layer from outside to inside.
Dive deeper →System Design
System Design: Building a URL Shortener Like Bit.ly
Step-by-step system design walkthrough for a URL shortener covering requirements, API design, database schema, and scaling strategies.
Dive deeper →System Design: Building a Distributed Rate Limiter
Step-by-step system design walkthrough for Building a Distributed Rate Limiter covering architecture, scaling, and trade-offs.
See full guide →System Design: Real-Time Chat Application
Step-by-step system design walkthrough for Real-Time Chat Application covering architecture, scaling, and trade-offs.
Get started →System Design: Social Media News Feed
Step-by-step system design walkthrough for Social Media News Feed covering architecture, scaling, and trade-offs.
Learn more →System Design: Web Search Engine Architecture
Step-by-step system design walkthrough for Web Search Engine Architecture covering architecture, scaling, and trade-offs.
View details →System Design: Video Streaming Platform Like Netflix
Step-by-step system design walkthrough for Video Streaming Platform Like Netflix covering architecture, scaling, and trade-offs.
Learn more →System Design: Online Payment Processing System
Step-by-step system design walkthrough for Online Payment Processing System covering architecture, scaling, and trade-offs.
View details →System Design: Push Notification Service
Step-by-step system design walkthrough for Push Notification Service covering architecture, scaling, and trade-offs.
View details →System Design: Distributed Caching System
Step-by-step system design walkthrough for Distributed Caching System covering architecture, scaling, and trade-offs.
Explore guide →System Design: Load Balancer from Scratch
Step-by-step system design walkthrough for Load Balancer from Scratch covering architecture, scaling, and trade-offs.
Continue reading →System Design: Distributed Web Crawler
Step-by-step system design walkthrough for Distributed Web Crawler covering architecture, scaling, and trade-offs.
Explore guide →System Design: Ride-Sharing Service Like Uber
Step-by-step system design walkthrough for Ride-Sharing Service Like Uber covering architecture, scaling, and trade-offs.
View details →System Design: Typeahead Suggestion System
Step-by-step system design walkthrough for Typeahead Suggestion System covering architecture, scaling, and trade-offs.
See full guide →System Design: Distributed Key-Value Store
Step-by-step system design walkthrough for Distributed Key-Value Store covering architecture, scaling, and trade-offs.
Learn more →System Design: Online Ticket Booking System
Step-by-step system design walkthrough for Online Ticket Booking System covering architecture, scaling, and trade-offs.
Continue reading →System Design: Cloud File Storage Like Google Drive
Step-by-step system design walkthrough for Cloud File Storage Like Google Drive covering architecture, scaling, and trade-offs.
Get started →System Design: Scalable Email Service
Step-by-step system design walkthrough for Scalable Email Service covering architecture, scaling, and trade-offs.
Dive deeper →System Design: API Gateway and Management
Step-by-step system design walkthrough for API Gateway and Management covering architecture, scaling, and trade-offs.
Dive deeper →System Design: Metrics and Monitoring System
Step-by-step system design walkthrough for Metrics and Monitoring System covering architecture, scaling, and trade-offs.
Continue reading →System Design: Social Graph Service
Step-by-step system design walkthrough for Social Graph Service covering architecture, scaling, and trade-offs.
View details →System Design: Image Hosting and CDN Service
Step-by-step system design walkthrough for Image Hosting and CDN Service covering architecture, scaling, and trade-offs.
View details →System Design: E-Commerce Platform Architecture
Step-by-step system design walkthrough for E-Commerce Platform Architecture covering architecture, scaling, and trade-offs.
Get started →System Design: Proximity and Location Service
Step-by-step system design walkthrough for Proximity and Location Service covering architecture, scaling, and trade-offs.
Continue reading →System Design: Distributed Message Queue Like Kafka
Step-by-step system design walkthrough for Distributed Message Queue Like Kafka covering architecture, scaling, and trade-offs.
Get started →System Design: Authentication and Authorization Service
Step-by-step system design walkthrough for Authentication and Authorization Service covering architecture, scaling, and trade-offs.
Continue reading →System Design: Content Delivery Network Architecture
Step-by-step system design walkthrough for Content Delivery Network Architecture covering architecture, scaling, and trade-offs.
Explore guide →System Design: Real-Time Analytics Platform
Step-by-step system design walkthrough for Real-Time Analytics Platform covering architecture, scaling, and trade-offs.
View details →System Design: Collaborative Calendar Service
Step-by-step system design walkthrough for Collaborative Calendar Service covering architecture, scaling, and trade-offs.
See full guide →System Design: Food Delivery Application
Step-by-step system design walkthrough for Food Delivery Application covering architecture, scaling, and trade-offs.
View details →System Design: Centralized Logging System
Step-by-step system design walkthrough for Centralized Logging System covering architecture, scaling, and trade-offs.
View details →Data Structures & Algorithms
Graph Algorithms Every Developer Should Know for DSA Interviews
Deep dive into BFS, DFS, Dijkstra, topological sort, and union-find with practical interview examples and implementations.
View details →Dynamic Programming Patterns for Coding Interviews
Break down the most common DP patterns including knapsack, LCS, LIS, and grid problems with step-by-step explanations.
Dive deeper →Binary Search Tree: Insert, Delete, and Search Operations
Master binary search tree: insert, delete, and search operations for coding interviews with detailed explanations and implementations.
Dive deeper →Linked List Reversal Patterns and Techniques
Master linked list reversal patterns and techniques for coding interviews with detailed explanations and implementations.
Get started →Hash Table Design and Collision Resolution Strategies
Master hash table design and collision resolution strategies for coding interviews with detailed explanations and implementations.
View details →Heap Sort and Priority Queue Internals
Master heap sort and priority queue internals for coding interviews with detailed explanations and implementations.
Dive deeper →Merge Sort: Divide and Conquer Mastery
Master merge sort: divide and conquer mastery for coding interviews with detailed explanations and implementations.
Get started →Quicksort and Partition Scheme Variations
Master quicksort and partition scheme variations for coding interviews with detailed explanations and implementations.
Dive deeper →AVL Trees: Self-Balancing with Rotations
Master avl trees: self-balancing with rotations for coding interviews with detailed explanations and implementations.
Get started →Red-Black Tree Fundamentals and Insertions
Master red-black tree fundamentals and insertions for coding interviews with detailed explanations and implementations.
Learn more →Trie Data Structure: Deep Dive and Applications
Master trie data structure: deep dive and applications for coding interviews with detailed explanations and implementations.
Explore guide →Disjoint Set Union: Path Compression and Union by Rank
Master disjoint set union: path compression and union by rank for coding interviews with detailed explanations and implementations.
Explore guide →Minimum Spanning Tree: Kruskal and Prim Algorithms
Master minimum spanning tree: kruskal and prim algorithms for coding interviews with detailed explanations and implementations.
Explore guide →Shortest Path Algorithms: Dijkstra vs Bellman-Ford vs Floyd-Warshall
Master shortest path algorithms: dijkstra vs bellman-ford vs floyd-warshall for coding interviews with detailed explanations and implementations.
Continue reading →Topological Sort: Kahn BFS vs DFS Approaches
Master topological sort: kahn bfs vs dfs approaches for coding interviews with detailed explanations and implementations.
See full guide →Essential Bit Manipulation Tricks for Interviews
Master essential bit manipulation tricks for interviews for coding interviews with detailed explanations and implementations.
Get started →Converting Recursion to Iteration Systematically
Master converting recursion to iteration systematically for coding interviews with detailed explanations and implementations.
View details →Amortized Analysis: Understanding True Operation Costs
Master amortized analysis: understanding true operation costs for coding interviews with detailed explanations and implementations.
Explore guide →Counting Sort and Radix Sort: Linear Time Sorting
Master counting sort and radix sort: linear time sorting for coding interviews with detailed explanations and implementations.
Dive deeper →Fenwick Tree (Binary Indexed Tree) Explained
Master fenwick tree (binary indexed tree) explained for coding interviews with detailed explanations and implementations.
See full guide →String Matching: KMP, Rabin-Karp, and Z-Algorithm
Master string matching: kmp, rabin-karp, and z-algorithm for coding interviews with detailed explanations and implementations.
Explore guide →Graph Representations: Adjacency List vs Matrix
Master graph representations: adjacency list vs matrix for coding interviews with detailed explanations and implementations.
Get started →Stack and Queue: Array and Linked List Implementations
Master stack and queue: array and linked list implementations for coding interviews with detailed explanations and implementations.
Get started →Time and Space Complexity Analysis for Interviews
Master time and space complexity analysis for interviews for coding interviews with detailed explanations and implementations.
See full guide →Binary Tree Traversals: Inorder, Preorder, Postorder, Level-Order
Master binary tree traversals: inorder, preorder, postorder, level-order for coding interviews with detailed explanations and implementations.
Get started →Mock Interviews
The Complete Mock Interview Preparation Guide
How to structure and get the most out of mock interviews for technical, behavioral, and system design rounds.
Continue reading →Top 10 Tips for Mock Coding Interviews
Essential guidance on top 10 tips for mock coding interviews for interview preparation.
View details →Behavioral Interview Questions: Mock Practice List
Essential guidance on behavioral interview questions: mock practice list for interview preparation.
Explore guide →Whiteboard Interview Strategies and Best Practices
Essential guidance on whiteboard interview strategies and best practices for interview preparation.
View details →How to Run a System Design Mock Interview
Essential guidance on how to run a system design mock interview for interview preparation.
Continue reading →Managing Interview Anxiety: Techniques That Work
Essential guidance on managing interview anxiety: techniques that work for interview preparation.
See full guide →Preparing for Pair Programming Interviews
Essential guidance on preparing for pair programming interviews for interview preparation.
Dive deeper →Time Management During Coding Interviews
Essential guidance on time management during coding interviews for interview preparation.
Explore guide →The Art of Asking Clarifying Questions in Interviews
Essential guidance on the art of asking clarifying questions in interviews for interview preparation.
Continue reading →Post-Interview Review: Learning from Every Interview
Essential guidance on post-interview review: learning from every interview for interview preparation.
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