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107 lines
3.7 KiB
Java
107 lines
3.7 KiB
Java
/*This Java program,implements Adjacency list.In graph theory and computer science, an adjacency list representation of a graph is a collection of unordered lists, one for each vertex in the graph. Each list describes the set of neighbors of its vertex.*/
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import java.util.HashMap;
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import java.util.InputMismatchException;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Map;
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import java.util.Scanner;
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public class AdjacencyList
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{
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private Map<Integer,List<Integer>> Adjacency_List;
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public AdjacencyList(int number_of_vertices)
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{
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Adjacency_List = new HashMap<Integer, List<Integer>>();
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for (int i = 1; i <= number_of_vertices; i++)
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{
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Adjacency_List.put(i, new LinkedList<Integer>());
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}
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}
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public void setEdge(int source, int destination)
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{
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if (source > Adjacency_List.size() || destination > Adjacency_List.size())
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{
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System.out.println("the vertex entered in not present ");
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return;
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}
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List<Integer> slist = Adjacency_List.get(source);
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slist.add(destination);
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List<Integer> dlist = Adjacency_List.get(destination);
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dlist.add(source);
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}
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public List<Integer> getEdge(int source)
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{
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if (source > Adjacency_List.size())
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{
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System.out.println("the vertex entered is not present");
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return null;
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}
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return Adjacency_List.get(source);
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}
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public static void main(String...arg)
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{
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int source, destination;
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int number_of_edges, number_of_vertices;
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int count = 1;
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Scanner scan = new Scanner(System.in);
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try
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{
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System.out.println("Enter the number of vertices and edges in graph");
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number_of_vertices = scan.nextInt();
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number_of_edges = scan.nextInt();
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AdjacencyList adjacencyList = new AdjacencyList(number_of_vertices);
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System.out.println("Enter the edges in graph Format : <source index> <destination index>");
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while (count <= number_of_edges)
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{
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source = scan.nextInt();
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destination = scan.nextInt();
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adjacencyList.setEdge(source, destination);
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count++;
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}
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System.out.println("the given Adjacency List for the graph \n");
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for (int i = 1; i <= number_of_vertices; i++)
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{
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System.out.print(i+"->");
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List<Integer> edgeList = adjacencyList.getEdge(i);
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for (int j = 1; ; j++ )
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{
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if (j != edgeList.size())
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System.out.print(edgeList.get(j - 1 ) + "->");
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else
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{
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System.out.print(edgeList.get(j - 1 ));
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break;
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}
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}
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System.out.println();
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}
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}
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catch (InputMismatchException inputMismatch)
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{
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System.out.println("Error in Input Format. \nFormat : <source index> <destination index>");
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}
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scan.close();
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}
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}
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/*
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Enter the number of vertices and edges in graph
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4 5
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Enter the edges in graph Format : <source index> <destination index>
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1 2
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2 3
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3 4
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4 1
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1 3
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the given Adjacency List for the graph
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1->2->4->3
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2->1->3
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3->2->4->1
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4->3->1
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