# Graphs A Level Resources

## A Level Computer Science: Graphs

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#### What is a graph in computer science?

A graph in computer science is a set of vertices (or nodes) and edges (or arcs) that connect pairs of vertices. It's a way to represent relationships between different entities and is considered a non-linear data structure.

#### What are directed and undirected graphs?

In a directed graph, edges have a direction, meaning they go from one vertex to another but not the other way around. In an undirected graph, edges don't have a direction, meaning if there is an edge from vertex A to vertex B, there is also an edge from vertex B to vertex A.

#### What is a weighted graph?

A weighted graph is a graph in which each edge has a numerical value or "weight" associated with it. These weights could represent things like distance, cost, or time. In contrast, an unweighted graph has edges with no weights assigned to them.

#### How are graphs implemented in programming?

Graphs can be implemented in various ways, including adjacency matrices, adjacency lists, and object-oriented representations. The choice of implementation often depends on the specific use-case, like the density of the graph or the operations you'll be performing on it.

#### What does it mean to traverse a graph?

Traversing a graph means visiting all the vertices of the graph and examining all the edges. This is often done to solve problems like finding the shortest path, detecting cycles, or simply to apply some operation to each vertex. There are different algorithms for graph traversal like Depth-First Search (DFS) and Breadth-First Search (BFS).