Dijkstra's algorithm in java

Dijkstra's algorithm in java

package dijkstra;

import java.util.Scanner;

public class Demo {

int no_nodes;

int matrix[][];

int s; // source

int d[];// distance

int p[]; // parent

boolean visited[]; // to track visited node

Scanner in=new Scanner(System.in);

public void input(){

System.out.println("Enter no. of Nodes");

no_nodes=in.nextInt();

matrix=new int[no_nodes][no_nodes];

d=new int[no_nodes];

p=new int[no_nodes];

visited=new boolean[no_nodes];

System.out.println("Enter connection matrix");

System.out.print("  ");

for(int i=0;i<no_nodes;i++){

char ch=(char)(65+i);

System.out.print(ch+"\t");

}

System.out.println();

for(int i=0;i<no_nodes;i++){

System.out.print((char)(65+i));

for(int j=0;j<no_nodes;j++){

matrix[i][j]=in.nextInt();

}

System.out.println();

}

}

public void initialize(){

for(int i=0;i<no_nodes;i++){

d[i]=1000; // infinity

p[i]=-1 ;// nil for parents

visited[i]=false;

}

d[s]=0;

}

public int findVertex(){

int min=1000;

int vertex=0;

for(int i=0;i<no_nodes;i++){

if(visited[i]==false && d[i]<min){

min=d[i];

vertex=i;

}

visited[vertex]=true;

}

return vertex;

}

public void algorithm(){

System.out.println("Enter source");

s=in.nextInt();

initialize();

int c=no_nodes;

while(c>0){

// find vertex to go

int vertex=findVertex();

c--;

for(int i=0; i<no_nodes;i++){

if(matrix[vertex][i]>0){

// relax

int dis=matrix[vertex][i];

if(dis+d[vertex]<d[i]){

d[i]=dis+d[vertex];

p[i]=vertex;

}

}

}

}

System.out.println("Source= "+(char)(65+s));

System.out.println();

System.out.print(" ");

System.out.print("\tD"+"\tP\n");

for(int i=0;i<no_nodes;i++){

System.out.print((char)(65+i)+"\t");

System.out.print(d[i]+"\t");

System.out.print((char)(65+p[i])+"\n");

}

}

public static void main(String args[]){

Demo obj=new Demo();

obj.input();

obj.algorithm();

}

}