Stop grinding lists.
Ride the map.
Every one of the 500 interview problems is a stop on one of 50 stations. A station is one code shape you memorize once; each stop is that shape plus one twist. In Python, JavaScript, C++ or Java.
✓ Lines 1 and 2 are open right here, no account needed · instant access · cancel anytime
- 12lines, one topic each, in prerequisite order
- 50stations, one code shape each
- 500stops, each a solved problem
- 55shapes to memorize, 4 to 16 lines each
Read it like a metro map: a colored line is one topic, a ring is a station (one code shape you memorize), a dot is a stop (one problem). The little car rides the gold Start Here express: 14 stations that unlock the rest. Click a line to zoom in, a station to open its shape, a stop to see the problem. Drag to pan.
The videos are free. Here is what isn't.
Hundreds of walkthroughs are public on @InterviewPatternMastery and stay free. Pro is the system that turns them into something you can memorize and reuse: ten things you only get on the map.
55 code shapes. 477 lines of Python in total.
That is the whole hard-memorization budget: 50 stations plus 5 recursive or iterative twins, 4 to 16 lines each, 8.7 on average. Everything else is a twist you can derive. Pick a shape, switch the language, notice the variable names never change.
PM 67 · Longest Substring Without Repeating Characters.
Stop 1 of 14 on the Grow-Shrink Window station. The walkthrough is one of the free videos; the station, the twist and the pre-loaded solution are what Pro adds around it.
Same problem, same station, four languages. Across the 500 stops: Python walkthroughs for 498; Java, JavaScript and C++ for every one of the 100 Pattern Mastery stops (100 / 100 / 100). Every station has its shape in all four.
- The stationGrow-Shrink Window, 6 lines. Memorized once, used by 14 stops.
- The twistState: a set of seen characters.
invalid(): a duplicate exists. Record: the longest valid window. - In the editorCanonical solution and baseline pre-loaded, tests for this problem, run in the browser, mark watched for review.
Pick a company. See its route on the same map.
Each route is built from how often that company's loops hit a station, not from a marketing list. Badges count the company's problems per station; filled badges are must-do. Interview Intel packs add the loop itself: stages, reported questions, and the station each one maps to.
Interviewing somewhere not listed? Pro members request a pack and get it within 48 hours. How packs work →
Everything, for less than one hour of a coach.
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- All 12 lines: 50 stations with the animated, line-synced scene and the shape in Python, JavaScript, C++ and Java
- 500 stops with canonical + baseline solutions pre-loaded, tests, in-browser Python runner
- Walkthrough video on every stop (Python), and in Java, JavaScript and C++ on all 100 Pattern Mastery stops
- Progress rings, the Start Here express, Recall mode and spaced review
- 24 company routes on the map, Interview Intel packs, request any company (48h)
- AI tutor, notes, study plans, Job Hunter resume tool, and everything we ship while you are subscribed
Questions people ask before buying.
What exactly do I memorize?
55 code shapes: 50 stations plus 5 twins (the recursive or iterative form of the same move), 4 to 16 lines each, 477 lines in total. Each shape has an invariant and a table of the only things that change between its stops. You never memorize a problem; you memorize the station and learn to spot the twist. See all of them above.
Why not just watch the YouTube videos?
Please do, they are free. A video shows one problem; the map tells you which of the 50 stations it is, what changed, which 13 other stops share the shape, and what to ride next. Pro also puts the tested solution in an editor you can run, tracks what you have cleared, and lets you rebuild the shape from memory with Recall mode.
Is Java really supported?
Yes. Every one of the 50 station shapes is written in Java with the same variable names as the other three languages, problem pages show the Java shape, and all 100 Pattern Mastery stops have a per-problem Java walkthrough video, streamed from the same library as the Python ones. Beyond the first 100, the Python walkthrough plus the Java shape covers the same steps.
What if the video uses a different approach than the canonical shape?
Both are on the page. The station form is first (it is the one you memorize), the form the video walks through is labeled "in the video", and any form still being recorded is labeled "video pending". Every form is tested against the problem's cases.
Can I cancel?
Yes. It is a yearly subscription you can cancel any time from the account menu; you keep access until the end of the paid year.
What is free?
Lines 1 and 2 on the map above: 11 stations with the animated scene, the shape in all four languages and every stop listed. The YouTube channel is free and stays free.