Sign in Get started

Now with AI Tutor — explains every problem like a friend

Data Structures & Algorithms
— in Plain English

Learn DSA from scratch with beginner-friendly explanations, hands-on practice problems — and an AI Tutor that explains every problem in plain English, step by step, on demand.

Create Free Account Explore topics

25 DSA topics

300+ problems

14 patterns

AI tutor

live code runner

~/dsafun · two-sum.js

JS·PY·JAVA·passed

// Two Sum — O(n) hash map
function twoSum(nums, target) {
  const seen = new Map();
  for (let i = 0; i < nums.length; i++) {
    const need = target - nums[i];
    if (seen.has(need))
      return [seen.get(need), i];
    seen.set(nums[i], i);
  }
}

stdout

$ node two-sum.js

[0, 1]

runtime 12ms

memory 38.6 mb

cases 57 / 57

› ready for next problem

Meet your AI Tutor

Stuck on a problem? Hit Teach Me and get a personalised explanation — generated just for you, right in the page.

Plain English

Breaks down exactly what the problem is asking, without the jargon.

Step-by-step

Walks you through the thinking process before showing any code.

Worked examples

Traces a real input through every step so you see exactly how it works.

AI Tutor included with Gold and Premium plans

Problem of the Day

Implement Trie

MediumTriesAmazonGoogleMeta

Pricing

Yearly. No subscription traps.

One charge a year. Renews only if you let it.

Top 20 FAANG problems · open to everyone

· 12 foundational topics (Beginner DS + Algorithms)
· Full solutions & explanations
· 20 FAANG problems
· Community discussion

50 FAANG problems · AI Tutor on every problem

Buy me a coffee

· Everything in Basic
· All 25 topics (Advanced DS + Algorithms)
· Practice code editor (JS / Python / Java)
· 50 FAANG problems
· AI Tutor on every problem

All 150 FAANG problems · unlimited AI Tutor

· Everything in Gold
· 150 FAANG problems
· Community discussion
· Practice code editor
· DSA Patterns Cheat Sheet
· AI Tutor on every problem

Master Every DSA Pattern in 7 Days

Buy me lunch subscribers only

Sliding Window · Two Pointers · BFS/DFS · DP · Greedy — copy-paste templates for every pattern with recognition cues

Buy me lunch — £9.99

Explore Data Structures (Free)

Data StructureBeginner

Arrays

A row of lockers for your data

10 LeetCode 3–5 hours

Data StructureBeginner

Linked List

Connected nodes forming a chain

10 LeetCode 4–6 hours

Data StructureBeginner

Stacks

Last In First Out structure

10 LeetCode 3–4 hours

Data StructureBeginner

Queues

First In First Out structure

10 LeetCode 3–4 hours

Data StructureBeginner

HashMap & HashSet

Fast lookup using keys

13 LeetCode 4–6 hours

Data StructureIntermediate

Binary Trees

Hierarchical node-based structure

13 LeetCode 6–8 hours

Data StructureIntermediate

Heaps

Priority-based tree structure

10 LeetCode 5–7 hours

Data StructureIntermediate

Graphs (BFS/DFS)

Nodes connected with edges

12 LeetCode 6–9 hours

Data StructureAdvanced

AVL Trees

Self-balancing binary search trees

10 LeetCode 8–12 hours

Data StructureAdvanced

Tries

Prefix-based word lookup tree

10 LeetCode 6–10 hours

Data StructureAdvanced

Segment Trees

Range queries and updates in O(log n)

3 LeetCode 8–12 hours

Data StructureAdvanced

Union-Find (DSU)

Track connected components efficiently

4 LeetCode 5–8 hours

Explore Algorithms (Free)

AlgorithmBeginner

Sorting Algorithms

Arrange data in order

10 LeetCode 6–10 hours

AlgorithmBeginner

Search Algorithms

Find items efficiently

10 LeetCode 5–9 hours

AlgorithmBeginner

String Manipulation

Transform and analyze text

10 LeetCode 6–10 hours

AlgorithmAdvanced

Advanced Graph Algorithms

Shortest paths and connectivity

10 LeetCode 8–15 hours

AlgorithmIntermediate

Dynamic Programming

Break problems into overlapping subproblems

18 LeetCode 8–12 hours

AlgorithmBeginner

Two Pointers

Two indices moving through data in tandem

5 LeetCode 4–6 hours

AlgorithmIntermediate

Sliding Window

Maintain a moving subarray over data

6 LeetCode 5–7 hours

AlgorithmIntermediate

Backtracking

Explore all possibilities, prune dead ends

10 LeetCode 6–9 hours

AlgorithmIntermediate

Greedy Algorithms

Make the locally optimal choice at each step

6 LeetCode 5–7 hours

AlgorithmIntermediate

Bit Manipulation

Operate directly on binary representations

5 LeetCode 4–6 hours

AlgorithmIntermediate

Recursion & Divide and Conquer

Split problems, solve halves, combine results

5 LeetCode 5–8 hours

AlgorithmIntermediate

Matrix & 2D Arrays

Grid traversal, rotation, and DP on 2D

5 LeetCode 5–7 hours

AlgorithmIntermediate

Intervals

Merge, insert and count overlapping ranges

5 LeetCode 4–6 hours

💬

Send us a message

We usually reply within 24 hours

DSA Fun — Learn Data Structures & Algorithms with an AI Tutor