Data Structures in Practice
Like Duolingo, but for Data Structures in Practice. Tomo turns the whole topic into a game you play five minutes a day, until it actually sticks.
For the part of you with thirty open tabs that never became anything.
25 levels across 3 sections, about 50 minutes end to end, roughly 10 days at five minutes a day. It moves through Working with Everyday Sequences and Lookups, Structuring Hierarchies and Networks, and Selecting Structures and Avoiding Traps. It starts from scratch.
Free forever · No credit card · iPhone & Android
Key ideas in Data Structures in Practice
- Scanning an unsorted list means checking items one by one until finding a match
- A key-value map jumps straight to the exact location in a single step regardless of collection size
- The map takes the plain-text key as input
- The hash function mathematically converts that key into a specific numeric index
- The map reads the value directly out of the memory slot at that index
- Two distinct keys can produce the exact same index (a collision)
- Maps handle collisions gracefully using strategies like chaining multiple values in a bucket or finding the next open slot
- Maps power fast lookups by pairing a unique identifier (key) directly to its payload (value)
- Web sessions pair a token to account details so authentication takes one step
- Routers map typed URLs directly to the code that renders the page
- Hash maps reserve extra empty slots in memory to keep lookups fast and collisions low
- Hash maps scatter data across memory and do not maintain the natural insertion or alphabetical order of items
- Lists use less memory per item and preserve an orderly sequence
- Array items sit side by side in a single unbroken block of memory
- The computer calculates the exact memory location using index multiplied by item size
- Accessing any index takes the same instant calculation regardless of position
You've tried the other tabs
Thirty open tabs. Four facts you actually kept.
You watched. You nodded. By Sunday it was gone.
One answer, then back to scrolling.
Eight weeks. You meant to finish. You didn't.
Tomo gives Data Structures in Practice the Duolingo treatment: levels, streaks, and quick quizzes that test what you just learned. That game loop is what the tabs above never had, so it's the one you actually finish.
Here's what playing it feels like
A real question from this course. Take your best guess.
Why is finding a toy in a key-value map so fast?
Get it right to open this lesson and 24 more in the app.
Where Data Structures in Practice takes you
Discover how real software organizes, stores, and accesses data at scale. Explore everyday structures like hash maps, trees, and queues, and learn to make fast, reliable architectural choices.
- 1
Working with Everyday Sequences and Lookups
- Instant Lookups with Key-Value Maps
- Ordered Sequences and the Shifting Problem
- Strict Flow: Stacks and Queues
- 2
Structuring Hierarchies and Networks
- Pointers and Node Chains in Linked Lists
- Hierarchical Data and Search Trees
- Interconnected Systems with Graphs
- 3
Selecting Structures and Avoiding Traps
- Architectural Trade-Offs in Production
- Common Data Structure Anti-Patterns
3 sections · 8 units · 25 levels. Built to play, not to enroll.
You pick the voice
Data Structures in Practice is taught in the Explain Like I'm 5 style: no big words. promise.. Want a different feel? In the app you can spin up the same topic in any of Tomo's teaching styles. Same facts, totally different vibe.
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