101OneNoughtOne

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All practice problemsCoding, design and hands-on challenges.Repository CodingHands-onFix bugs and build in a real codebase.Code ReviewHands-onFind risks and explain your verdict.Data structures & algorithmsCore patterns to advanced algorithms.Machine learningImplement ML and numerical methods.SQL & databasesQueries, data and analytical problems.HLD system designScalable architecture and tradeoffs.LLD system designObjects, interfaces and behavior.GATE papersBranch-wise previous year papers and worked solutions.AptitudeAptitude topics and exam practice.AI interview prepRehearse interviews with an AI tutor.Online compilerWrite and run code in your browser.

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Learning pathsConnect lessons, visualizers and practical challenges.Algorithm visualizersStep through algorithms and see how they work.ReadingRead books, notes and research papers with AI.Daily current affairsUnderstand the news, save notes and revise the brief.Data structures & algorithmsLearn the foundations of efficient problem solving.Machine learningBuild mathematical intuition and explore ML concepts.SQL & databasesUnderstand data models, queries and transactions.System designStudy architecture, distributed systems and object design.
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101OneNoughtOne

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BUILD YOUR FOUNDATION

A little structure.
A lot of possibility.

Go beyond memorizing answers. Build a deeper understanding through connected lessons, hands-on practice and checkpoints along the way.

Learn the idea.
Put it into practice.

23learning paths
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Learn at your own pace

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23 paths to explore

Beginner

SQL Practice: Queries to Analytics

101OneNoughtOneLEARNING PATH

Progress from filtering and joins to analytical windows, time-series queries and recursive SQL, with focused database lessons and a data-export repository capstone.

149.2 hours3 lessons305 problems
  • SELECT, WHERE, ORDER BY
  • JOINs
  • GROUP BY and aggregation
3 more topics
  • Subqueries and CTEs
  • Window functions
  • Query optimization
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Beginner

Data Structures & Algorithms

101OneNoughtOneLEARNING PATH

Build strong algorithmic foundations, trace algorithms visually, solve progressive DSA problems, and apply invariants in real repository and code-review exercises.

231.7 hours279 lessons67 problems15 visualizers
  • Arrays & Strings
  • Linked Lists
  • Trees & Graphs
5 more topics
  • Sorting & Searching
  • Dynamic Programming
  • Recursion & Backtracking
  • Bit Manipulation
  • Advanced Data Structures
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Intermediate

High-Level System Design

101OneNoughtOneLEARNING PATH

Move from architecture fundamentals to concrete system-design cases, then test consistency, failure recovery and authorization decisions through repository coding and review.

268 hours268 lessons51 problems
  • Scalability and reliability
  • Distributed systems
  • Storage and databases
5 more topics
  • Caching and performance
  • Messaging and eventing
  • Security and observability
  • Cloud architecture
  • System design interviews
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Intermediate

Low-Level System Design

101OneNoughtOneLEARNING PATH

Learn object-oriented design and design patterns, solve low-level design cases, and practise state transitions, persistence and error handling in real repositories and code reviews.

209.9 hours246 lessons44 problems
  • Object-oriented design
  • SOLID principles
  • Design patterns
5 more topics
  • API and persistence design
  • Concurrency fundamentals
  • Clean architecture
  • Testing and maintainability
  • LLD interview preparation
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Intermediate

Database Management Systems

101OneNoughtOneLEARNING PATH

Study relational design, SQL, transactions and storage, reinforce query concepts with SQL problems, and apply consistency and analytical exports in repository coding and review.

221.4 hours252 lessons26 problems
  • Relational Model
  • SQL Mastery
  • ER Modeling
5 more topics
  • Normalization
  • Transactions & ACID
  • Indexing & B-Trees
  • Query Optimization
  • Distributed Databases
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Advanced

Machine Learning Patterns

101OneNoughtOneLEARNING PATH

Master Machine Learning from fundamentals to advanced techniques through 19 comprehensive chapters. This path covers 318 carefully curated problems spanning linear algebra, probability, classical ML, deep learning, reinforcement learning, and more.

151.8 hours15 lessons317 problems
  • Linear Algebra & Calculus
  • Probability & Statistics
  • Classical ML Algorithms
5 more topics
  • Neural Networks
  • Deep Learning
  • Reinforcement Learning
  • NLP & Computer Vision
  • MLOps & Deployment
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Intermediate

Computer Networks

101OneNoughtOneLEARNING PATH

Master Computer Networks from fundamentals to advanced protocols. This comprehensive path covers the OSI model, TCP/IP, routing, switching, network security, and modern networking with 46 chapters and 1200+ pages.

200 hours240 lessons
  • OSI & TCP/IP Models
  • Ethernet & Switching
  • IP Addressing & Subnetting
5 more topics
  • Routing Protocols
  • Transport Layer (TCP/UDP)
  • Application Protocols
  • Network Security
  • Wireless Networks
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Intermediate

Operating Systems

101OneNoughtOneLEARNING PATH

Master Operating Systems from fundamentals to advanced concepts. This comprehensive path covers processes, threads, memory management, file systems, I/O, virtualization, and distributed systems with 47 chapters and 1201+ pages.

196.8 hours236 lessons
  • Process Management
  • Thread Synchronization
  • Memory Management
5 more topics
  • Virtual Memory
  • File Systems
  • I/O Systems
  • Virtualization
  • Distributed Systems
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Advanced

Machine Learning

101OneNoughtOneLEARNING PATH

Learn the mathematical and engineering foundations of machine learning, explore executable visualizers, implement algorithms, and validate dataset releases in repository exercises.

249.3 hours277 lessons39 problems
  • Linear Algebra & Calculus
  • Probability & Statistics
  • Supervised Learning
5 more topics
  • Unsupervised Learning
  • Neural Networks
  • Deep Learning
  • Reinforcement Learning
  • ML Engineering
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Intermediate

Data Structures & Algorithms Patterns

101OneNoughtOneLEARNING PATH

Master Data Structures and Algorithms through 15 chapters of coding patterns. From Two Pointers to Dynamic Programming, this path covers 320 carefully curated problems organized by technique for optimal learning progression.

174.3 hours26 lessons323 problems15 visualizers
  • Two Pointers & Sliding Window
  • Binary Search Techniques
  • Stack & Queue Patterns
5 more topics
  • Tree & Graph Algorithms
  • Greedy Algorithms
  • Backtracking
  • Dynamic Programming
  • Bit Manipulation
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Intermediate

Algorithms in Real Systems

101OneNoughtOneLEARNING PATH

Connect data-structure and algorithm foundations to search, scheduling, dependency engines and production repository bugs. Learn the invariant, trace it, solve it, then implement and review it in an existing system.

167.8 hours102 lessons83 problems11 visualizers
  • Complexity and invariants
  • Hashing and windows
  • Ordering and intervals
5 more topics
  • Trees and indexes
  • Dependencies and shortest paths
  • Dynamic programming
  • Constraint search
  • Repository implementation
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Intermediate

Backend Engineering Foundations

101OneNoughtOneLEARNING PATH

Build a service-engineering foundation from HTTP and relational modeling through API boundaries, authorization, transactions, tests, caching and operational delivery. Apply each layer in repository coding and code review.

184 hours127 lessons53 problems
  • HTTP and DNS
  • API contracts
  • Object and domain design
5 more topics
  • Relational modeling and SQL
  • Authorization
  • Transactions and retries
  • Testing
  • Caching and operations
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Advanced

Reliable Services & Transactional Workflows

101OneNoughtOneLEARNING PATH

Engineer reliable state transitions under retries, concurrency, partial failure and delayed events. Combine database and distributed-systems foundations with implementation, review and system-design practice.

153.5 hours76 lessons65 problems
  • Atomicity and isolation
  • Idempotency and receipts
  • Versioned state
4 more topics
  • Outboxes and delivery
  • Time and ordering
  • Replication and coordination
  • Observability and recovery
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Intermediate

Data Quality & Analytics Engineering

101OneNoughtOneLEARNING PATH

Build trustworthy analytics from relational modeling and SQL through data validation, event-time processing, reproducible reporting and reviewed dataset releases. Practice query correctness and pipeline invariants in real repositories.

129.6 hours59 lessons87 problems
  • Relational grain and keys
  • SQL and null semantics
  • Joins and aggregation
5 more topics
  • Windows and cohorts
  • Data preparation
  • Historical event visibility
  • Quality gates
  • Reproducible releases
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Intermediate

Repository Debugging & Code Review

101OneNoughtOneLEARNING PATH

Learn a disciplined reproduce–trace–repair–verify–review workflow. Progress from boundary bugs to authorization, versioned state, parsing, algorithms, atomic recovery and complete product regressions in existing repositories.

123.6 hours38 lessons106 problems
  • Reproduction and regression tests
  • Module and data-flow tracing
  • Validation and authorization
4 more topics
  • State and ordering
  • Algorithmic debugging
  • Recovery
  • Independent code review
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Beginner

Computer Science Interview Foundations

101OneNoughtOneLEARNING PATH

Build a broad technical interview foundation in algorithms, operating systems, networks, databases, object design, testing and security. Connect explanations to visual traces, coding problems, design cases and repository work.

302.8 hours241 lessons54 problems7 visualizers
  • Complexity and data structures
  • Recursion and dynamic programming
  • Processes and synchronization
6 more topics
  • Memory and I/O
  • TCP, DNS, HTTP and TLS
  • SQL and database design
  • Transactions and indexes
  • Object and system design
  • Testing and security
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Advanced

Concurrent State & Distributed Coordination

101OneNoughtOneLEARNING PATH

Progress from threads and synchronization to transactional concurrency, replicated logs and causal state. Apply the foundations to bounded queues, commit rules, stale writers and failure recovery.

118.8 hours66 lessons39 problems
  • Threads and synchronization
  • Deadlocks
  • Transactional concurrency
3 more topics
  • Replicated logs
  • Causal state
  • Failure recovery
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Intermediate

Database Internals & Query Performance

101OneNoughtOneLEARNING PATH

Study how relational data becomes storage pages, tree indexes, execution plans and recoverable transactions. Practice SQL semantics, B+ tree repairs, query reasoning and transactional workflows.

143.8 hours97 lessons34 problems
  • Relational semantics
  • Storage and pages
  • B+ trees and indexes
4 more topics
  • Query plans and operators
  • Isolation and MVCC
  • Logging and recovery
  • Database operations
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Intermediate

HTTP Integrations & Contract Engineering

101OneNoughtOneLEARNING PATH

Build reliable client–service integrations by understanding DNS, transport, HTTP caching, URI resolution, typed payloads, authorization and retry contracts. Repair and review real protocol and compatibility defects.

122.2 hours55 lessons66 problems
  • DNS and transport
  • HTTP semantics
  • URI resolution
4 more topics
  • Caching and validators
  • Typed schema evolution
  • API authorization
  • Idempotent integration
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Intermediate

Production Debugging & Recovery

101OneNoughtOneLEARNING PATH

Investigate service failures from symptom to evidence and root cause. Study execution, memory, I/O and observability, then repair protocol, stale-state and partial-failure incidents with regression coverage.

119.8 hours59 lessons48 problems
  • Process and resource diagnostics
  • Memory and I/O
  • Evidence and observability
4 more topics
  • Protocol decoding
  • State reconstruction
  • Atomic recovery
  • Incident communication
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Advanced

Search, Parsing & Dependency Engines

101OneNoughtOneLEARNING PATH

Build algorithmic depth through text search, parsing, automata and incremental dependency engines. Connect data-structure lessons to concrete correctness, invalidation and evaluation rules in existing repositories.

91.7 hours33 lessons64 problems
  • Text representation
  • Tries and search
  • Expression parsing
4 more topics
  • Grammar analysis
  • Automata
  • Dependency graphs
  • Incremental invalidation
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Intermediate

Full-Stack Product Engineering

101OneNoughtOneLEARNING PATH

Trace product behavior across the browser, API and durable data. Practice resource eligibility, authoritative planning, settlement and analytics in native full-stack repositories with regression tests and code review.

84.8 hours36 lessons50 problems
  • Client and server boundaries
  • Domain contracts
  • API validation
4 more topics
  • Authoritative planning
  • Persistence and reload
  • Settlement and analytics
  • Accessibility and privacy
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Intermediate

Applied ML: Data, Models & Evaluation

101OneNoughtOneLEARNING PATH

Develop practical ML judgment from numerical foundations and reproducible data preparation through baseline models, evaluation and safe data releases. Combine implementation problems, visualizers and analytical repository labs.

106.3 hours49 lessons57 problems
  • Numerical foundations
  • Data preparation
  • Reproducible validation
4 more topics
  • Baseline models
  • Classification and regression metrics
  • Robust statistics
  • Dataset release controls
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