Search Tech Journey

Find topics, journeys and posts

Series · 65 sessions · ~81 hours

LeetCode — From Basics to Interview-Ready

LeetCode is a motor skill, not a knowledge skill. Reading about two pointers teaches you nothing; reproducing the template cold, under a timer, six times, teaches you everything. This series is pattern-first: each session takes one pattern apart, then grinds five problems that are the same pattern wearing different clothes. Zero assumed — session one starts at “how do you read a problem statement”.

Read the hub →Start with L01
Sessions
65
Phases
5
Per session
75 min
Cadence
Alt. days

The five rules

  1. 1. Pattern before problem. You learn the shape, then meet it five times. Random problem selection is the single biggest waste of grinding hours.
  2. 2. Write the template from memory. Every session opens with a blank file. If you can't reproduce the skeleton cold, you don't know it yet.
  3. 3. The two-attempt rule. Fifteen minutes stuck → read the editorial → close it → re-solve from scratch the next day. Never copy-paste-move-on.
  4. 4. Narrate before you type. If you can't explain the approach in ninety seconds, you don't have an approach — you have a hunch.
  5. 5. The spaced queue is the whole game. Everything solved returns at +7, +21, +60 days. Re-solving is where the pattern actually lands.

Phase 0 — Foundations

How to even do this

L01–L06
  1. L01The LeetCode Game — How to Read a Problem
  2. L02Big-O in Practice — Counting, Not Vibes
  3. L03Python for Speed — The 20 Idioms That Matter
  4. L04Arrays & Strings — In-Place Discipline
  5. L05Hashing — Your Default Weapon
  6. L06UMPIRE — The Problem-Solving Framework

Phase 1 — Core patterns

The 80% of interviews

L07–L32
  1. L07Two Pointers I — Opposite Ends
  2. L08Two Pointers II — Same Direction & Fast-Slow
  3. L09Sliding Window I — Fixed Size
  4. L10Sliding Window II — Variable Size
  5. L11Sliding Window III — With Counts
  6. L12Prefix Sums & Difference Arrays
  7. L13Binary Search I — The Template
  8. L14Binary Search II — Rotated & 2D
  9. L15Binary Search III — On the Answer
  10. L16Stacks — LIFO & Matching
  11. L17Monotonic Stack
  12. L18Queues & Monotonic Deques
  13. L19Linked Lists I — Traversal & Reversal
  14. L20Linked Lists II — Cycles, Middle, Reorder
  15. L21Recursion & the Call Stack
  16. L22Trees I — DFS Traversals
  17. L23Trees II — BFS / Level Order
  18. L24Trees III — BST Properties
  19. L25Trees IV — Paths & Accumulators
  20. L26Heaps & Top-K
  21. L27Graphs I — Representation & DFS
  22. L28Graphs II — BFS & Shortest Path
  23. L29Graphs III — Topological Sort
  24. L30Graphs IV — Union-Find (DSU)
  25. L31Backtracking I — Subsets & Combinations
  26. L32Backtracking II — Constraint Grids

Phase 2 — Dynamic programming

The wall most people hit

L33–L44
  1. L33DP I — Recognising Overlapping Subproblems
  2. L34DP II — 1D Linear
  3. L35DP III — Take / Skip Decisions
  4. L36DP IV — Subsequences (LIS / LCS)
  5. L37DP V — 0/1 Knapsack
  6. L38DP VI — Unbounded Knapsack
  7. L39DP VII — 2D Grid
  8. L40DP VIII — String DP / Edit Distance
  9. L41DP IX — Palindromes
  10. L42DP X — Interval DP
  11. L43DP XI — State Machine
  12. L44DP XII — Bitmask DP

Phase 3 — Advanced & specialised

The long tail that shows up anyway

L45–L56
  1. L45Tries — Prefix Trees
  2. L46Bit Manipulation
  3. L47Math & Number Theory
  4. L48Intervals
  5. L49Greedy — And Proving It Works
  6. L50Matrix Manipulation
  7. L51Design I — Composing for O(1)
  8. L52Design II — Streams & Time
  9. L53Sorting & Custom Comparators
  10. L54Segment Trees & Fenwick (BIT)
  11. L55String Algorithms
  12. L56Advanced Graphs

Phase 4 — Interview simulation

Pressure, not knowledge

L57–L65
  1. L57Mock Set 1 — Mixed Easy/Medium, 45 min
  2. L58Mock Set 2 — Narrated & Recorded
  3. L59Blind 75 Sweep — Gap Audit
  4. L60Weak-Pattern Intensive
  5. L61Mock Set 3 — One Hard, 45 min
  6. L62Company-Tagged — Microsoft & Amazon
  7. L63Senior-Flavour Coding
  8. L64Contest Simulation
  9. L65Final Audit + Maintenance Plan
Work through them in order. The phases build on each other — Phase 2 assumes you can already classify a Medium into a pattern in under a minute, which is exactly what Phase 1 trains.