data structures & algorithms · java · 3D

DSA you can touch.

From “I freeze on DSA rounds” to “I know exactly which pattern this is” — one interactive chapter at a time.

start chapter 01 →failed before? make my planwhy DSA still matters
chapters
38
3D simulations
302
interview problems
343

Ctrl K search anything · ? shortcuts

assembling the map…

see it

Every structure in 3D

Step through algorithms with your keyboard. Orbit, zoom, change the input. Nothing is a black box.

say it

Plain English first

The idea in three lines, an analogy, and the exact words to use in an interview.

solve it

Brute → optimal, in Java

Every solution compiled and tested. Raw implementations next to the Collections Framework.

land it

Interview-ready

Company tags, must-do lists, pattern triggers, traps and follow-up questions.

  1. 1736Graph (vertices + edges) and the adjacency listLeonhard Euler
  2. 1945Merge sortJohn von Neumann
  3. 1953Hash tableHans Peter Luhn; Gene Amdahl, Elaine M. McGraw (née Boehme), Nathaniel Rochester, Arthur Samuel (IBM); Arnold Dumey; W. Wesley Peterson
  4. 1956 (idea) · 1959 (paper)Dijkstra's algorithmEdsger W. Dijkstra
  5. 2002TimSort (Java's object sort)Tim Peters (Python) · Joshua Bloch (Java port, Java 7)
see the whole story →

The course

confidence0%

just starting — that's the hardest step

0/38 chapters · 0/343 problems

Java for DSA

Write and debug the Java that DSA interviews actually need, without fighting the language.

  1. 01 What Happens in Memory
  2. 02 Arrays & Strings in Java
  3. 03 OOP for DSA & Design Rounds
  4. 04 Fast I/O, Judges & Debugging
  5. 05 Java Toolkit & Collections

Thinking tools

Approach any unseen problem calmly, measure code with Big-O, and think recursively.

  1. 06 Mindset & Problem Solving
  2. 07 Big-O & Complexity
  3. 08 Recursion
  4. 09 Math & Number Theory

Linear patterns

Turn O(n²) loops into O(n) scans with the patterns behind most interview questions.

  1. 10 Arrays & Strings
  2. 11 Matrices & Simulation
  3. 12 Two Pointers
  4. 13 Sliding Window
  5. 14 Hashing & Prefix Sums
  6. 15 Linked Lists
  7. 16 Stacks & Monotonic Stack
  8. 17 Queues & Deques
  9. 18 Binary Search
  10. 19 Sorting
  11. 20 String Parsing & Expression Evaluation

Trees & graphs

Think in hierarchies and networks: traversals, heaps, tries, shortest paths, dependencies.

  1. 21 Tree Traversals
  2. 22 Tree Recursion
  3. 23 Binary Search Trees
  4. 24 Heaps & Priority Queues
  5. 25 Tries
  6. 26 Graphs: BFS & DFS
  7. 27 Shortest Paths
  8. 28 Union-Find & Minimum Spanning Trees
  9. 29 Topological Sort
  10. 30 Advanced Graphs: Euler Paths, Bridges & SCCs

Paradigms

Explore choices systematically, know when greedy is safe, and build DP from recursion.

  1. 31 Backtracking
  2. 32 Greedy Algorithms
  3. 33 Intervals
  4. 34 Bit Manipulation
  5. 35 Dynamic Programming
  6. 36 DP Patterns

Expert

Design data structures on the spot and handle range-query and string-matching rounds.

  1. 37 Design Data Structures
  2. 38 Segment Trees, Fenwick & String Matching

How to use this without burning out

  1. One chapter, one sitting. Read the 30-second idea, then play with the simulation until you can predict the next step (press P for predict mode).
  2. Code the brute force first. It's allowed. It's how every expert starts.
  3. Then climb the ladder. Better → optimal. Say out loud why each step is faster.
  4. Redo must-dos from a blank page after 1, 3, 7, 16 and 35 days. Spaced repetition beats grinding hundreds of problems.