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Commit 7abf247

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Kruskal’s algorithm in Java
1 parent 08423dc commit 7abf247

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4 files changed

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-0
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4 files changed

+206
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lines changed

‎Graph/kruskal/Demo.java

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/*
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Copyright (C) Deepali Srivastava - All Rights Reserved
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This code is part of DSA course available on CourseGalaxy.com
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*/
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package kruskal;
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public class Demo
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{
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public static void main(String [] args)
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{
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UndirectedWeightedGraph g = new UndirectedWeightedGraph();
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g.insertVertex("Zero");
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g.insertVertex("One");
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g.insertVertex("Two");
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g.insertVertex("Three");
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g.insertVertex("Four");
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g.insertVertex("Five");
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g.insertVertex("Six");
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g.insertVertex("Seven");
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g.insertVertex("Eight");
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g.insertVertex("Nine");
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g.insertEdge("Zero","One", 19);
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g.insertEdge("Zero","Three", 14);
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g.insertEdge("Zero","Four", 12);
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g.insertEdge("One","Two", 20);
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g.insertEdge("One","Four", 18);
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g.insertEdge("Two","Four", 17);
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g.insertEdge("Two","Five", 15);
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g.insertEdge("Two","Nine", 29);
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g.insertEdge("Three","Four", 13);
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g.insertEdge("Three","Six", 28);
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g.insertEdge("Four","Five", 16);
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g.insertEdge("Four","Six", 21);
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g.insertEdge("Four","Seven", 22);
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g.insertEdge("Four","Eight", 24);
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g.insertEdge("Five","Eight", 26);
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g.insertEdge("Five","Nine", 27);
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g.insertEdge("Six","Seven", 23);
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g.insertEdge("Seven","Eight", 30);
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g.insertEdge("Eight","Nine", 35);
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g.kruskals();
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}
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}

‎Graph/kruskal/Edge.java

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/*
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Copyright (C) Deepali Srivastava - All Rights Reserved
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This code is part of DSA course available on CourseGalaxy.com
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*/
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package kruskal;
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public class Edge implements Comparable<Edge>
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{
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int u;
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int v;
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int wt;
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public Edge(int u, int v, int wt)
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{
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this.u=u;
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this.v=v;
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this.wt=wt;
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}
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public int compareTo(Edge obj)
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{
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if(wt == obj.wt)
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return 0;
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else if(wt>obj.wt)
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return 1;
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else
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return -1;
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}
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}
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/*
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Copyright (C) Deepali Srivastava - All Rights Reserved
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This code is part of DSA course available on CourseGalaxy.com
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*/
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package kruskal;
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import java.util.PriorityQueue;
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public class UndirectedWeightedGraph
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{
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public final int MAX_VERTICES = 30;
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int n;
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int e;
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int [][] adj;
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Vertex [] vertexList;
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private static final int NIL= -1;
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public UndirectedWeightedGraph()
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{
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adj = new int[MAX_VERTICES][MAX_VERTICES];
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vertexList = new Vertex[MAX_VERTICES];
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}
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public void kruskals()
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{
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PriorityQueue<Edge> pq = new PriorityQueue<Edge>();
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int u,v;
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for(u=0; u<n; u++)
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for(v=0; v<u; v++)
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{
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if(adj[u][v]!=0)
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pq.add(new Edge(u,v,adj[u][v]));
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}
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for(v=0; v<n; v++)
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vertexList[v].father = NIL;
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int v1,v2,r1=NIL,r2=NIL;
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int edgesInTree=0;
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int wtTree=0;
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while(!pq.isEmpty() && edgesInTree<n-1)
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{
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Edge edge = pq.remove();
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v1=edge.u;
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v2=edge.v;
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v=v1;
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while(vertexList[v].father!=NIL)
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v=vertexList[v].father;
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r1=v;
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v=v2;
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while(vertexList[v].father!=NIL)
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v=vertexList[v].father;
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r2=v;
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if(r1!=r2) /*Edge (v1,v2) is included*/
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{
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edgesInTree++;
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System.out.println(vertexList[v1] + "," + vertexList[v2] );
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wtTree += edge.wt;
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vertexList[r2].father=r1;
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}
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}
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if(edgesInTree < n-1)
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throw new RuntimeException("Graph is not connected, no spanning tree possible\n");
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System.out.println("Weight of Minimum Spanning Tree is " + wtTree);
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}
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private int getIndex(String s)
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{
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for(int i=0; i<n; i++)
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if(s.equals(vertexList[i].name))
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return i;
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throw new RuntimeException("Invalid Vertex");
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}
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public void insertVertex(String name)
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{
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vertexList[n++] = new Vertex(name);
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}
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/*Insert an edge (s1,s2) */
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public void insertEdge(String s1, String s2, int wt)
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{
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int u = getIndex(s1);
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int v = getIndex(s2);
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if(adj[u][v] !=0 )
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System.out.print("Edge already present");
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else
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{
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adj[u][v]=wt;
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adj[v][u]=wt;
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e++;
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}
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}
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}
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‎Graph/kruskal/Vertex.java

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/*
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Copyright (C) Deepali Srivastava - All Rights Reserved
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This code is part of DSA course available on CourseGalaxy.com
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*/
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package kruskal;
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public class Vertex
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{
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String name;
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int father;
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Vertex(String name)
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{
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this.name = name;
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}
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public String toString()
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{
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return name;
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}
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}

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