Math and Geometry (S1)

Coordinate geometry, rectangles, polygons Modular arithmetic and large numbers

Sorting, Greedy and Searching (S2)

Greedy with sorting and exchange arguments Two pointers and sliding window Prefix sums and difference arrays II Binary search on the answer Hash maps and frequency counting

Brute Force and Data Structures (S3)

Complete search and bounds analysis Constructive algorithms Stacks and queues Priority queues and sets Disjoint Set Union

Strings and Graphs

String processing patterns BFS/DFS on structured graphs Trees and rooted traversal Functional graphs and cycle detection Counting and combinatorics

Strings and Graphs

BFS/DFS on structured graphs

frequent

Work in progress

This module is still being written — the content here is a placeholder. This guide is open source, and contributions are welcome.

Contribute on GitHub — help write this module by opening a pull request.

String processing patterns

String processing patterns, anchored on 2024 S2 *Heavy-Light Composition* and 2025 S2 *Cryptogram Cracking Club*

Trees and rooted traversal

Trees and rooted traversal — anchored on 2016 S3 *Phonomenal Reviews*

On this page

BFS/DFS on structured graphs