LearnAndCode
Data Structures & AlgorithmsLearning
Problem solving · FOCUSED GUIDE

Learn Data Structures & Algorithms.

Learn the patterns behind interview problems, then implement them in JavaScript, Java, C#/.NET, or Python.

A pattern-first DSA path

Understand the pattern. Trace it. Code it. Explain it.

Build interview confidence from Big O and core data structures to graphs, dynamic programming, and advanced patterns. Learn the idea once, then see how to implement it in your preferred language.

Start with the fundamentalsPractice DSA questions
  1. 01

    Understand

    Clarify the input, output, constraints, and edge cases.

  2. 02

    Choose a pattern

    Match the problem to hashing, two pointers, BFS/DFS, DP, or another reusable pattern.

  3. 03

    Explain and verify

    Trace an example, write clean code, test edge cases, and state time and space complexity.

New to DSA?

Follow Core concepts in order. Start with complexity, arrays, maps, linked lists, stacks, and queues before trees, graphs, and dynamic programming.

Preparing for an interview?

Use the priority labels, solve the 30-problem checklist, and practise explaining your approach and complexity before writing code.

Choose your next lesson

Complete DSA learning path

Search by problem or pattern, filter the core guide by stage, or select a language for implementation examples.

Language
Stage

75 lessons shown

Start hereFoundations & core patterns

4 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. How to prepare for DSA interviews

    Core rule

    Core conceptsMust know2 min
  2. Big O notation

    What it is

    Core conceptsMust know2 min
  3. Arrays and strings

    Arrays

    Core conceptsMust know2 min
  4. Hashing and maps

    What it is

    Core conceptsMust know2 min
Data structuresLinear data structures

3 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. Linked list

    What it is

    Core conceptsMust know2 min
  2. Stack and queue

    Stack

    Core conceptsMust know2 min
  3. Recursion and backtracking

    Recursion

    Core conceptsMust know2 min
Data structuresTrees, heaps & graphs

3 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. Trees and binary search trees

    Binary tree

    Core conceptsMust know2 min
  2. Heap and priority queue

    What it is

    Core conceptsMust know2 min
  3. Graphs

    Graph representation

    Core conceptsMust know2 min
AlgorithmsAlgorithms & problem-solving patterns

5 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. Dynamic programming

    What it is

    Core conceptsMust know2 min
  2. Greedy algorithms

    What it is

    Core conceptsMust know2 min
  3. Sorting and searching

    Sorting

    Core conceptsMust know2 min
  4. Bit manipulation

    Important concepts

    Core conceptsMust know2 min
  5. Sliding window and two pointers

    Sliding window

    Core conceptsMust know2 min
AdvancedAdvanced patterns & priorities

2 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. Advanced patterns

    Monotonic stack

    Core conceptsShould know2 min
  2. Common interview topics by priority

    Must know

    Core conceptsMust know2 min
Interview prepInterview practice & revision

2 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. 30 interview questions to practice

    1. Two Sum

    Core conceptsMust know2 min
  2. Final interview advice

    Explain the approach before coding.

    Core conceptsGood to know2 min
Language practiceJavaScript implementations

14 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. JavaScript DSA basics

    Common JavaScript structures

    JavaScriptShould know2 min
  2. Arrays and strings in JavaScript

    Common questions

    JavaScriptShould know2 min
  3. Hashing and maps in JavaScript

    Why it matters

    JavaScriptShould know2 min
  4. Linked list in JavaScript

    Node structure

    JavaScriptShould know2 min
  5. Stack and queue in JavaScript

    Stack using array

    JavaScriptShould know2 min
  6. Recursion and backtracking in JavaScript

    Common questions

    JavaScriptShould know2 min
  7. Trees and BST in JavaScript

    Tree node

    JavaScriptShould know2 min
  8. Heap and priority queue in JavaScript

    Custom min-heap

    JavaScriptShould know2 min
  9. Graphs in JavaScript

    Graph representation

    JavaScriptShould know2 min
  10. Dynamic programming in JavaScript

    Common questions

    JavaScriptShould know2 min
  11. Greedy and binary search in JavaScript

    Common greedy questions

    JavaScriptGood to know2 min
  12. Sliding window and two pointers in JavaScript

    Sliding window

    JavaScriptGood to know2 min
  13. Important JavaScript DSA interview topics

    1. Arrays and strings

    JavaScriptGood to know2 min
  14. JavaScript interview-friendly practice list

    Two Sum

    JavaScriptGood to know2 min
Language practiceJava implementations

14 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. Java DSA basics

    Common data structures in Java

    JavaShould know2 min
  2. Arrays and strings in Java

    Key operations

    JavaShould know2 min
  3. Hashing and maps in Java

    Why it matters

    JavaShould know2 min
  4. Linked list in Java

    Node structure

    JavaShould know2 min
  5. Stack and queue in Java

    Stack

    JavaShould know2 min
  6. Recursion and backtracking in Java

    Common questions

    JavaShould know2 min
  7. Trees and BST in Java

    Tree node

    JavaShould know2 min
  8. Heaps and priority queue in Java

    Important class

    JavaShould know2 min
  9. Graphs in Java

    Graph representation

    JavaShould know2 min
  10. Dynamic programming in Java

    Common Java DP problems

    JavaShould know2 min
  11. Sorting and searching in Java

    Sorting

    JavaGood to know2 min
  12. Bit manipulation in Java

    Common operations

    JavaGood to know2 min
  13. Important interview questions for Java

    1. Explain difference between ArrayList and LinkedList.

    JavaGood to know2 min
  14. Best Java DSA interview practice list

    Must know

    JavaGood to know2 min
Language practiceC# / .NET implementations

14 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. .NET DSA fundamentals

    Common .NET collections

    C# / .NETShould know2 min
  2. Arrays and strings in C#

    Common questions

    C# / .NETShould know2 min
  3. Hashing in .NET

    Why it matters

    C# / .NETShould know2 min
  4. Linked list in C#

    Node structure

    C# / .NETShould know2 min
  5. Stack and queue in .NET

    Stack

    C# / .NETShould know2 min
  6. Recursion and backtracking in C#

    Common questions

    C# / .NETShould know2 min
  7. Trees and BST in C#

    Tree node

    C# / .NETShould know2 min
  8. Heap and priority queue in .NET

    PriorityQueue<T> usage

    C# / .NETShould know2 min
  9. Graphs in C#

    Common questions

    C# / .NETShould know2 min
  10. Dynamic programming in C#

    Common questions

    C# / .NETShould know2 min
  11. Sorting and searching in C#

    Sorting

    C# / .NETGood to know2 min
  12. Sliding window and two pointers in C#

    Common questions

    C# / .NETGood to know2 min
  13. Important .NET interview questions

    1. Difference between List<T> and Array?

    C# / .NETGood to know2 min
  14. Best .NET DSA practice list

    Must know

    C# / .NETGood to know2 min
Language practicePython implementations

14 focused lessons with explanations, patterns, examples, practice problems, and interview guidance.

  1. Python DSA basics

    Common Python structures

    PythonShould know2 min
  2. Arrays and strings in Python

    Common questions

    PythonShould know2 min
  3. Hashing and maps in Python

    Why it matters

    PythonShould know2 min
  4. Linked list in Python

    Node structure

    PythonShould know2 min
  5. Stack and queue in Python

    Stack

    PythonShould know2 min
  6. Recursion and backtracking in Python

    Common questions

    PythonShould know2 min
  7. Trees and BST in Python

    Tree node

    PythonShould know2 min
  8. Heap and priority queue in Python

    Built-in heapq

    PythonShould know2 min
  9. Graphs in Python

    Graph representation

    PythonShould know2 min
  10. Dynamic programming in Python

    Common questions

    PythonShould know2 min
  11. Binary search and greedy in Python

    Binary search

    PythonGood to know2 min
  12. Sliding window and two pointers in Python

    Common questions

    PythonGood to know2 min
  13. Important Python interview topics

    1. List vs tuple vs set vs dict

    PythonGood to know2 min
  14. Best Python DSA practice list

    Must know

    PythonGood to know2 min