A Graph is a non-linear data structure consisting of nodes and edges. The nodes are sometimes also referred to as vertices and the edges are lines or arcs that connect any two nodes in the graph.
In this tutorial, you will learn what a Graph Data Structure is. Also, you will find representations of a graph.
A graph data structure is a collection of nodes that have data and are connected to other nodes.
Let's try to understand this through an example. On facebook, everything is a node. That includes User, Photo, Album, Event, Group, Page, Comment, Story, Video, Link, Note...anything that has data is a node.
Every relationship is an edge from one node to another. Whether you post a photo, join a group, like a page, etc., a new edge is created for that relationship.
All of facebook is then a collection of these nodes and edges. This is because facebook uses a graph data structure to store its data.
More precisely, a graph is a data structure (V, E) that consists of
A collection of vertices VA collection of edges E, represented as ordered pairs of vertices (u,v)
Graph Terminology
Adjacency: A vertex is said to be adjacent to another vertex if there is an edge connecting them. Vertices 2 and 3 are not adjacent because there is no edge between them.
Path: A sequence of edges that allows you to go from vertex A to vertex B is called a path. 0-1, 1-2 and 0-2 are paths from vertex 0 to vertex
2.Directed Graph: A graph in which an edge (u,v) doesn't necessarily mean that there is an edge (v, u) as well. The edges in such a graph are represented by arrows to show the direction of the edge.
