You solved it.
Three weeks later, it is gone.

Recode brings back every LeetCode problem you solve right before you would forget it.

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Day 60: 92% recall after 2 short re-solves

25%50%75%100%90% targetSolvedDay 15Day 30Day 45Day 60

Modelled with FSRS-6 default parameters, one problem rated Good at each review.

Arrays in week one. Trees in week four. Group Anagrams feels new again.

Practising topic by topic builds momentum, then quietly erases whatever came first. Here is a typical month, with each topic solved once and never revisited.

  1. Week 1

    Arrays & Hashing

    Group Anagrams

    67%

  2. Week 2

    Two Pointers

    3Sum

    70%

  3. Week 3

    Linked List

    Reorder List

    74%

  4. Week 4

    Trees

    Validate Binary Search Tree

    88%

Recall at the end of week four, from the FSRS-6 forgetting curve after a single solve.

Solve once. Re-solve on cue.

  1. 1

    Encode

    Solve it on LeetCode, from NeetCode 150, Blind 75 or any of 464 company lists. Tick it here and the model starts tracking that memory.

  2. 2

    Elaborate

    Rate how it went and write the one-line insight that cracked it. Explaining the key idea in your own words makes it easier to retrieve later.

  3. 3

    Retrieve on schedule

    When predicted recall drifts down to 90%, it appears in Today. You rebuild the solution from memory, and each success stretches the next gap.

Sheet

  • Longest Consecutive SequenceMedium
  • Container With Most WaterMedium
  • Trapping Rain WaterHard

How did the re-solve go?

11dAgain
29dHard
314dGood
424dEasy

Each key shows when you would see the problem again. Hints and time taken cap the grade.

Today, mixed across patterns

  1. 1Koko Eating Bananas86%
  2. 2Course Schedule81%
  3. 3Daily Temperatures88%
  4. 4Coin Change74%

Inside one memory, from first solve to long-term.

Recode models every problem you solve with three numbers. Step through the life of one problem and watch them change, with the same model the scheduler runs.

D
2.1
1 to 10
S
2.3 d
days to 90%
R
100%
recall now
50%90%100%Day 0

Encoding

Solving a problem encodes a memory trace. The model describes it with two numbers set by how the solve went: difficulty D, how hard this problem is for you, and stability S, the number of days until your chance of recalling it falls to 90%. Rated Good, S starts at 2.3 days.

Two-component model of long-term memory: Woźniak, Gorzelańczyk & Murakowski, 1995

1/6

The science

Built on what memory research actually shows.

FSRS, not fixed intervals

The Free Spaced Repetition Scheduler, the model behind modern Anki, tracks how difficult each problem is for you and how stable your memory of it has become. It predicts the day your recall crosses your target and schedules the re-solve for that day, not a generic 1, 3, 7.

R(t) = (1 + f · t / S)−w

R
chance you can still solve it
S
stability, grows with each success
t
days since your last solve

Overdue? No penalty. A late success counts for more, because you recalled it against the odds.

Mixed beats blocked

63%mixed practice

20%one topic at a time

Test scores a week later when practice problems were interleaved versus grouped by type. Your review queue never puts two problems of the same pattern back to back.

Rohrer & Taylor, Instructional Science, 2007

Recall first, then look

Every review starts by naming the pattern from the title alone. Five-question drills train the same skill on problems you have not seen, which is what an interview actually tests.

  • 1Sliding Window
  • 2Two Pointers
  • 3Arrays & Hashing
  • 41-D DP

1,868 problems.
464 company lists.

Work through NeetCode 150 or Blind 75 in roadmap order, or target a company by what it asks most. A problem you solve once counts on every list it appears on.

  • Google242
  • Meta210
  • Amazon199
  • Microsoft188
  • Bloomberg188
  • Uber170
  • Apple168
  • TikTok164
  • Oracle145
  • Goldman Sachs140
  • LinkedIn128
  • Salesforce126
  • TCS116
  • Zoho113
  • Adobe112
  • Nvidia112
  • Walmart Labs111
  • IBM111
  • Yandex108
  • Flipkart106
  • Snap105
  • Accenture103
  • PayPal102
  • DE Shaw102
  • Yahoo101
  • Citadel97
  • Infosys95
  • DoorDash80

Questions

Do I need to give Recode my LeetCode password?

No. You solve on LeetCode and tick the box here. Optionally, link your public username and Recode will suggest ticks from your recent accepted submissions.

What if I skip a few days?

Nothing breaks. Overdue problems stay in the queue, weakest first, and the model accounts for the extra time. A daily budget in minutes keeps a backlog from turning into a wall.

Re-solving a problem I remember feels like a waste.

If it was easy, rate it Easy and it disappears for months. The point is to spend time only where memory is actually slipping.

Is it free?

Yes. Create an account and start with any sheet.

Keep what you learn.

Tick your first problem in under a minute.

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