Algorithms and Data Structures

VisiGrab

In-app purchases

About this app

VisiGrab is an interactive visualizer for algorithms and data structures. Every structure and algorithm is animated step by step, with matching implementation code in Java, Python, and C++, so you see exactly how the code changes the data.

Built for computer science students preparing for exams, self-taught developers filling gaps in CS fundamentals, and engineers getting ready for coding interviews.

Why VisiGrab

The theory behind data structures is available online for free. What is hard is building real intuition from textbooks and scattered tutorials. VisiGrab presents each topic in a structured sequence, from arrays to graph algorithms, so every concept builds on the previous one.

You don't just read about a rotation in an AVL tree or a relaxation step in Dijkstra's algorithm. You watch it happen, step forward and back, and compare each step with the code.

How Each Topic Works
• Theory: a short, focused explanation of the concept, without textbook overload
• Visualization: the algorithm runs step by step, and every step has its own description
• Practice: enter your own values, build trees, draw graphs, and see the result instantly
• Code: the implementation in Java, Python, and C++ right next to the animation

The animations are designed to be clear even before you read a single line of text.

Data Structures
• Array, Linked List, Doubly Linked List
• Stack, Queue
• Min-Heap
• Hash Table (chaining and open addressing)
• Binary Search Tree (BST), AVL Tree, Red-Black Tree, B-Tree
• Trie
• Graph, with a graph constructor to build your own

Algorithms
• Sorting: Bubble, Selection, Insertion, Merge, Heap, Quick Sort
• Tree traversals: pre-order, in-order, post-order, breadth-first (BFS)
• Insertion and deletion in BST, AVL, Red-Black Tree, and B-Tree
• Graph algorithms: BFS, DFS, Dijkstra's shortest path, Bellman-Ford
• Minimum spanning tree: Prim's and Kruskal's algorithms
• Topological Sort, Union-Find

Learn by Doing
• Build your own AVL and Red-Black trees and watch rotations keep them balanced
• Draw your own graph and run BFS, DFS, Dijkstra, Prim, or Kruskal on it
• Pause, step forward, and rewind any animation

Code in Java, Python, and C++
Every animation comes with its implementation in three languages. See the direct link between each line of code and what happens to the data. All implementations are open source on GitHub.

Coding Interview Preparation
VisiGrab covers the data structures and algorithms most often asked in technical interviews. Use it alongside LeetCode practice to understand the patterns behind the problems instead of memorizing solutions. Also useful for university algorithms courses and competitive programming.

Free to Start
Core topics are free. A one-time purchase unlocks all advanced topics, plus every future topic and update. No subscription, no ads, no popups.

Available in 10 Languages
English, German, French, Spanish, Portuguese, Polish, Ukrainian, Japanese, Korean, and Chinese (Simplified).

Study Anywhere
Works fully offline: on the train, between classes, or anywhere without a connection.

Made by a Developer and Mathematician
VisiGrab is built by an independent developer with a PhD in mathematics, teaching experience, and more than a decade of professional software development.

Ratings and reviews

Excellent app, great value! I'm a professional engineer, but learned mostly on the job, so I have a lot of gaps around algo/data struct/big O. I've been trying to learn and be able to name them all, and this app is awesome! What completely sold me on getting full access was the light bulb part on slide 17 of Arrays. That kind of granular information really helps me cement things together and it was wonderful to see that!

Great app so far! I would like to see some advanced algorithms as well. But it's ok to just getting started with algo and data structure.

This makes learning of data structures so much easier. The visuals and in-depth explanations help with getting the concept to "click".

What’s new

• Added B-Tree — add and remove keys, choose the maximum degree, and watch the nodes split, borrow and merge