DSA Field Notes
NeetCode · Algorithms and Data Structures for Beginners
12 topics · 34 lessons · Python

DSA Field Notes

Study notes for the NeetCode beginner course. Every topic page shows the mechanism in diagrams (orange marks what changed), gives Python that was actually run, and ends with a mistakes list, a practice order, and a self-check quiz. Read a page after the videos, then close it and solve.

Course map

Topics build on each other in this order. Each card names the NeetCode lessons it covers.

01 · LESSONS 1-4

Arrays

RAM, static and dynamic arrays, amortized O(1), stacks.

RAM · Static Arrays · Dynamic Arrays · Stacks
02 · LESSONS 5-7

Linked Lists

Nodes and pointers, head/tail, doubly linked, queues.

Singly · Doubly · Queues
03 · LESSONS 8-9

Recursion

Base case, call stack, one-branch and two-branch trees.

Factorial · Fibonacci
04 · LESSONS 10-13

Sorting

Insertion, merge, quick, bucket. Stability and O(n log n).

Insertion · Merge · Quick · Bucket
05 · LESSONS 14-15

Binary Search

Halve the search space: on an array, on a range, on the answer.

Search Array · Search Range
06 · LESSONS 16-21

Trees

Binary trees, BSTs, insert/remove, DFS orders, BFS, tree sets and maps.

Binary Tree · BST · Insert/Remove · DFS · BFS · Sets and Maps
07 · LESSON 22

Backtracking

Choose, explore, un-choose. Tree maze and path building.

Tree Maze
08 · LESSONS 23-25

Heap / Priority Queue

Complete tree in an array, push, pop, heapify in O(n), heapq.

Properties · Push and Pop · Heapify
09 · LESSONS 26-27

Hashing

Hash maps and sets, hash functions, resizing, collisions.

Hash Usage · Hash Implementation
10 · LESSONS 28-31

Graphs

Matrix, adjacency matrix, adjacency list. DFS and BFS on both.

Intro · Matrix DFS · Matrix BFS · Adjacency List
11 · LESSONS 32-33

Dynamic Programming

Memoization and tabulation: fibonacci, unique paths.

1-D DP · 2-D DP
12 · LESSON 34

Bit Manipulation

AND, OR, XOR, NOT, shifts, counting bits, masks.

Bit Operations

How to use a page

1. Watchthe NeetCode lesson 2. Readthe page once, slowly 3. Solvenotes closed 4. Self-checkanswer out loud step 3 is the one that builds skill; the pages exist to make step 3 possible
Notes are for after the video, not instead of practice. Each page ends with "Your next step today": one problem. Do that one before reading the next topic.
Reading the diagrams

Teal = a pointer or link that already existed. Orange = what changed in this step. Dashed grey = the old link that was replaced. Faded = never visited or no longer reachable. Red ∅ = None.

What is on every page

SectionWhat it gives you
WhyA real-world analogy, then the technical idea, then one diagram of the core mechanism.
One section per lessonEvery fact, example array and code snippet from the NeetCode lesson, with trace tables and diagrams.
PatternsThe 2-4 "moves" interviews test on this topic, each with a tested Python template.
Big-OOne table; green is good, red is bad; every asterisk explained.
MistakesThe bugs beginners actually write, with the fix, plus one-liners to say out loud in interviews.
Practice8-12 LeetCode problems in order, each tagged with the move it trains.
Self-check10-13 questions with hidden answers, including trace-it questions.

All Python on these pages was executed before publishing; the check scripts live in the checks/ folder of the repository. Content follows the NeetCode "Algorithms and Data Structures for Beginners" course; the diagrams, trace tables, patterns, mistakes and quizzes are original study material.