#146LeetCode
LRU Cache
Solve this problem on LeetCode, then record your outcome.
DSA revision tracker · Spaced repetition
Automate your DSA revision.
Log each problem you solve. Hash-It schedules when to redo it, so your revision time goes to the problems you're about to forget.
Get startedReview queue
2 quick recall and 1 full re-solve
Hard
#3 Quick recall
Longest Substring Without Repeating Characters
#21 Quick recall
Merge Two Sorted Lists
Try it — interact with the cards above
The problem
Tracking isn't revising
I was already logging every problem I solved, and I still had no idea what to revise. A list shows what you've done. It can't show which problem from last month is about to slip.
The system
Log once, revise on schedule
Hit to log a problem. Record the time, the core idea, and any mistakes. The next review is scheduled automatically based on how you performed.
How it works
Solve, log, and redo it when it's due.
1
Solve and log
Solve a problem on LeetCode. Log the time, the core insight, and what tripped you up.
2
System schedules
FSRS estimates when you're likely to forget the problem and puts it in your queue that day. No manual scheduling.
3
Re-solve and grow
Solve it cold and the gap before the next review grows, from days to weeks to months. Struggle and it comes back sooner.
Fig. 1. Cards move through your queue and return at widening intervals.
Spaced repetition, not guesswork
FSRS estimates when you're likely to forget each problem. You re-solve those first and leave alone the ones you still remember.
Fig. 2. Without review, recall drops to near zero. Spaced reviews keep it high with widening intervals.
Three review cadences
Due for review
Your next problems, in order
#146 · LRU Cache
Design
#3 · Longest Substring Without Repeating Characters
Sliding Window
#200 · Number of Islands
Graph
Weekly review
Recall first, then check your notes
Core idea
Try to recall the approach before revealing your saved note.
Monthly mock
A timed set from your weaker patterns
01Problem 01Unrevealed
02Problem 02Unrevealed
03Problem 03Unrevealed
04Problem 04Unrevealed
05Problem 05Unrevealed
Every day
Re-solve what is due
Work through problems as they begin to fade. Your next reviews are already in order.
Every week
Recall, then review
Test what you remember before revealing your notes, then choose problems for the week ahead.
End of the month
Measure your progress
Take a timed, blind set drawn from your weaker patterns and compare your results over time.
What an entry looks like
Every logged problem records the core insight and the exact mistakes that cost you time.
#146. LRU CacheHard
Hash TableLinked ListDesign
Core idea
Keep a doubly linked list for the recent items, and a hash map pointing to the list nodes for O(1) access.
Mistake log
- Forgot to remove the tail when capacity is reached.
- Didn't update the hash map when moving a node to the head.
Fig. 3. Each entry captures the idea and mistakes, not just the solve.
Targeted practice by pattern
Pick a pattern, get an easy–medium–hard set of problems you haven't solved yet. Shuffle until you find ones that challenge you, then log your attempt.
PatternTwo Pointers18 problems
PatternSliding Window12 problems
PatternBinary Search24 problems
PatternDynamic Prog.42 problems
PatternBFS / DFS31 problems
PatternBacktracking15 problems
PatternGreedy22 problems
PatternStack / Queue19 problems
Fig. 4. Hover a pattern to inspect its cluster. Pick a pattern, get a graded problem set.
Bring your LeetCode history or DSA sheet
Already solved a few hundred? Import them from a LeetCode screenshot, or upload the DSA sheet you track in Excel or CSV. Reviews are spread over 60 days so day one isn't a wall.
How to import
LeetCode · SolvedProgress
Accepted problems over time
Matched problems
#146LRU CacheMatched
#3Longest Substring…Matched
#200Number of IslandsMatched
| Problem | Title | Pattern | Time |
|---|---|---|---|
| #146 | LRU Cache | Design | 42m |
| #3 | Longest Substring | Sliding Window | 28m |
| #200 | Number of Islands | Graph | 35m |
problems.csv
number,title,pattern,time
146,LRU Cache,Design,42
3,Longest Substring,Sliding Window,28
200,Number of Islands,Graph,35Screenshot your LeetCode progress page, give it to any LLM along with our prompt, and paste the CSV it returns.
Real practice
Not a flashcard app
Anki reviews text. Hash-It reviews problems. You re-solve from scratch, on the real platform, under time pressure. The scheduling is the same science, and the practice is real.
Adaptive retention
Not a problem list
NeetCode and Grind 75 tell you what to solve first. Hash-It tells you what to solve again. Use any list to seed your log, and the schedule handles the revising.
Your interview prep shouldn't rely on memory alone.
Start logging problems. The system handles the rest.
Get startedFrequently asked questions about tracking DSA
New to spaced repetition for DSA? Read how to remember DSA problems.
A revision schedule for DSA. You log each problem after you solve it, and Hash-It tells you when to solve it again, a few days or weeks later, before you've forgotten how it works.
No. You keep solving on LeetCode, GeeksforGeeks or wherever you already practice. Hash-It keeps track of what you've done and what's due, and every problem in your queue links back to the original.
A spreadsheet shows what you've solved. It won't tell you that the graph problem from three weeks ago is about to slip. Hash-It works out when each problem is due from how it went last time, so you don't have to keep track of dates yourself.
No. Upload your DSA sheet as an Excel or CSV file, or, if you solve on LeetCode, import from a screenshot of your progress page. Imported problems are spread over the next 60 days, so you won't log in to 300 reviews on day one.
Open Today and do what's due. Most items are quick recall checks: read the title, remember the approach, check your notes. A couple are full re-solves where you actually code it again. By default that's at most two re-solves a day, and you can change that in settings.
That happens, and it's useful to know. Mark it as "Saw solution" and it comes back in a day or two instead of weeks later. Problems you keep missing show up as stuck, so you know which ones need a proper second look.
Nothing breaks. Missed problems wait in your queue, and the daily limit means you won't come back to 40 re-solves at once. It just takes a few days to catch up.
No, but it's worth it. One line on the key idea and one on what you got wrong is plenty. When the problem comes back, that's what you check yourself against.
It uses FSRS, the scheduling algorithm Anki offers. Solve something cold and the gap before you see it again gets longer each time, from days to weeks to months. Need a hint and it comes back sooner.
Yes. GeeksforGeeks links fill in the title and difficulty automatically, same as LeetCode. For problems from anywhere else, add the title and link yourself and everything else works the same.
Anyone studying DSA who wants a system for revising, whether that's interview prep or learning the topics. You keep solving wherever you already practice, and Hash-It handles when to redo each problem. It doesn't sync with LeetCode automatically, so you log problems as you solve them or import them from a screenshot or a CSV.
A Google account. Sign in, and you can log your first problem straight away. Your log is private to you.