# Introduction to Graph Data Structure

## Introduction

A graph is a non-linear kind of data structure made up of nodes or vertices and edges. The edges connect any two nodes in the graph, and the nodes are also known as vertices.

## Video Explanation

## Vertex/Node

**Vertex or node**, which represents elements. In the image below, the circles are the nodes, each node can represent a city, state, country, building, person, or any other object depending upon the problem.

## Edge

**Edges**, which represent relationships between elements. In the image below, the lines are the edges, each edge can represent a connection between two cities, persons, or any other object.

## Directed Graph

A directed graph also referred to as a digraph, is a set of nodes connected by edges, each with a direction.

## Undirected Graph

An undirected graph comprises a set of nodes and links connecting them. The order of the two connected vertices is irrelevant and has no direction. You can form an undirected graph with a finite number of vertices and edges.

## Weighted Graph

A graph `G = (V, E)`

is called a labeled or weighted graph because each edge has a value or weight representing the cost of traversing that edge.

## Unweighted Graph

A graph `G = (V, E)`

is called an unweighted graph because the edge only represents a connection between two nodes.

## Concluding Types of Graph

Similarly, you can form other combinations of **Unweighted and Directed Graph** and **Unweighted and Undirected Graph.**

**Path**

A **path** in a graph is a finite or infinite sequence of edges that joins a sequence of vertices which, by most definitions, are all distinct (and since the vertices are distinct, so are the edges).

## Cycle

A path that starts from a given vertex and ends at the same vertex is called a cycle.

**In**

**Note:****shown above, 0 -> 1 -> 2-> 0 is not a cycle.**

**the Directed Graph**## Indegree

In-degree of a vertex is the number of edges coming to the vertex.

## Outdegree

Out-degree of a vertex is the number of edges that are coming out from the vertex.

**, the number of Indegree and Outdegree of any vertex are equal.**

**Undirected Graph**Follow us on LinkedIn and connect with us on Discord in case you are stuck or have any questions.