- 15 Dec, 2025
Advanced Linked List, Stack & Queue
Week 21 notes: the harder linear-structure problems, where the trick is usually combining two structures. Reversing in k-groups, monotonic deques for sliding-window max, and the LRU cache.
- 08 Dec, 2025
Hashing & Prefix Sum Patterns
Week 20 notes: prefix sums plus a hash map is one of the combos I use most. O(1) range queries, counting subarrays with a target sum in one pass, 2-D prefix sums, and the difference array.
- 01 Dec, 2025
Two Pointers & Sliding Window (Advanced)
Week 19 notes: Phase 2 kicks off by pushing the two most reused array patterns to medium/hard. Variable windows with a shrink rule, the at-most/exactly counting trick, and multi-pointer partitioning.
- 24 Nov, 2025
Phase 1 Revision & Buffer
Week 18 is a breather. A topic-by-topic recap of Phase 1, a keyword-to-pattern cheat sheet, and the spaced-repetition plan I use for the problems that didn't stick.
- 17 Nov, 2025
Backtracking: An Intro
Week 17 notes: backtracking explores every candidate by building it up step by step and undoing dead ends. The choose/explore/un-choose template, and why pruning is everything.