# Gold

The topics below are not exhaustive for this division.

Contest problems may contain topics not covered in the guide, or topics listed under different divisions!

### Modules Progress

### Problems Progress

## Introductory Number Theory

## Dynamic Programming

Every (?) Gold and Platinum contest has at least one DP problem.

Introduction to DP

Very Frequent

Speeding up naive recursive solutions with memoization.

Updated: Last week

Knapsack DP

Not Frequent

Problems that can be modeled as filling a limited-size container with a subset of items.

Updated: Last week

Paths on Grids

Not Frequent

Counting the number of "special" paths on a grid, and how some string problems can be solved using grids.

(Optional) Longest Increasing Subsequence

Rare

Finding and using the longest increasing subsequence of an array.

Updated: Last week

## Graphs

Breadth First Search (BFS)

Not Frequent

Traversing a graph in a way such that vertices closer to the starting vertex are processed first.

Disjoint Set Union

Somewhat Frequent

The Disjoint Set Union (DSU) data structure allows you to add edges to an initially empty graph and test whether two vertices of the graph are connected.

Updated: Last week

Topological Sort

Rare

An ordering of vertices in a directed acyclic graph that ensures that a node is visited before every node it has a directed edge to.

Shortest Paths with Non-Negative Edge Weights

Somewhat Frequent

Introduces Bellman-Ford, Floyd-Warshall, Dijkstra.

Minimum Spanning Trees

Not Frequent

A subset of the edges of a connected, undirected, edge-weighted graph that connects all the vertices to each other of minimum total weight, where no cycles are allowed.

## Data Structures

Stacks

Rare

A data structures that only allows insertion and deletion at one end.

Updated: Last week

Sliding Window

Not Frequent

Maintaining data over consecutive subarrays.

Point Update Range Sum

Somewhat Frequent

Introduces Segment Tree, Binary Indexed Tree, and C++ Order Statistic Tree.

Updated: 2 days ago

## Trees

Euler Tour Technique

Not Frequent

Flattening a tree into an array to easily query and update subtrees.

Updated: Last week

DP on Trees - Introduction

Not Frequent

Using subtrees as subproblems.

Updated: 6 days ago

(Optional) DP on Trees - Solving For All Roots

Rare

Tree DP that uses the subtree from excluding each node's subtree.

## Hashing

Rarely required at this level, but still good to know.