### Graph Representation Using Adjacency List - The Coding Shala

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## Graph Representation Using Adjacency List

In this post, we will see how to represent a Graph using the Adjacency List. We used an array of lists. The Size of the array is the number of vertices and arr[i] represents the list of vertices adjacent to the ith vertex. The following example shows how to represent a graph using adjacency list:

### Graph Representation using Adjacency list Java Program

We have given the number of edges 'E' and vertices 'V' of a bidirectional graph. Now our task is to build a graph through the adjacency list and print the adjacency list for each vertex.

Example 1:

Input:

5 7 //vertex and edges

0 1

0 4

1 2

1 3

1 4

2 3

3 4

Output:

0-> 1-> 4

1-> 0-> 2-> 3-> 4

2-> 1-> 3

3-> 1-> 2-> 4

4-> 0-> 1-> 3

Java Code:

import java.util.*; class Graph{ int v; LinkedList<Integer>[] adjList; Graph(int v){ this.v = v; adjList = new LinkedList[v]; for(int i=0; i<v; i++){ adjList[i] = new LinkedList(); } } void Connect(int point1, int point2){ adjList[point1].add(point2); adjList[point2].add(point1); //bidirectional } void Display(){ for(int i=0; i<v; i++){ System.out.print(i); //print node for(Integer curr : adjList[i]){ System.out.print("-> "+curr); } System.out.println(); } } } class Main{ public static void main(String[] args){ Scanner sc = new Scanner(System.in); int tc = sc.nextInt(); //no. of test cases while(tc-->0){ int vertex = sc.nextInt(); int edges = sc.nextInt(); Graph g = new Graph(vertex); while(edges-->0){ int v1 = sc.nextInt(); int v2 = sc.nextInt(); g.Connect(v1, v2); } g.Display(); } } }

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