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Commit 30fb923

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Prim’s algorithm in Java
1 parent 1b42614 commit 30fb923

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3 files changed

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3 files changed

+199
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‎Graph/prims/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 prims;
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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.Prims();
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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 prims;
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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 TEMPORARY = 1;
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private static final int PERMANENT = 2;
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private static final int NIL= -1;
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private static final int INFINITY = 99999;
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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 Prims()
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{
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int c,v;
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int edgesInTree=0;
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int wtTree=0;
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for(v=0; v<n; v++)
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{
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vertexList[v].status = TEMPORARY;
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vertexList[v].length = INFINITY;
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vertexList[v].predecessor = NIL;
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}
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int root=0;
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vertexList[root].length = 0;
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while(true)
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{
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c = tempVertexMinL();
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if(c == NIL)
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{
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if(edgesInTree == n-1)
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{
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System.out.println("Weight of minimum spanning tree is " + wtTree);
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return;
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}
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else
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throw new RuntimeException("Graph is not connected, Spanning tree not possible");
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}
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vertexList[c].status = PERMANENT;
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/* Include edge ( vertexList[c].predecessor,c ) in the tree*/
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if(c!=root)
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{
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edgesInTree++;
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System.out.println("(" + vertexList[c].predecessor + "," + c + ")");
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wtTree = wtTree + adj[vertexList[c].predecessor][c];
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}
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for(v=0; v<n; v++)
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if(isAdjacent(c,v) && vertexList[v].status == TEMPORARY)
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if(adj[c][v] < vertexList[v].length)
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{
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vertexList[v].length = adj[c][v];
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vertexList[v].predecessor = c;
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}
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}/*End of while*/
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}
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int tempVertexMinL()
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{
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int min = INFINITY;
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int x = NIL;
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for(int v=0; v<n; v++)
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{
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if(vertexList[v].status == TEMPORARY && vertexList[v].length < min)
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{
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min=vertexList[v].length;
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x=v;
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}
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}
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return x;
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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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private boolean isAdjacent(int u, int v)
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{
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return (adj[u][v]!=0);
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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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}

‎Graph/prims/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 prims;
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public class Vertex
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{
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String name;
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int status;
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int predecessor;
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int length;
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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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