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

Sorting, Greedy and Searching (S2)

Hash maps and frequency counting

common

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.

Binary search on the answer

Binary search on the answer — anchored on 2021 S3 *Lunch Concert*

Complete search and bounds analysis

Complete search and bounds analysis — anchored on 2019 S3 *Arithmetic Square* and 2013 S3 *Chances of winning*

On this page

Hash maps and frequency counting