Merge pull request #30 from mk9440/master

Dijkshtra's Algorithm

Author: dynamitechetan

Dijkshtra.java

@@ -0,0 +1,56 @@
+/*
+@author  : Mayank K Jha
+
+*/
+
+
+public class Solution {
+
+public static void main(String[] args) throws IOException {
+	  Scanner in =new Scanner(System.in);
+	
+	int n=in.nextInt();             //n = Number of nodes or vertices
+        int m=in.nextInt();             //m = Number of Edges
+        long w[][]=new long [n+1][n+1]; //Adjacency Matrix  
+        
+	//Initializing Matrix with Certain Maximum Value for path b/w any two vertices 
+	for (long[] row: w)
+            Arrays.fill(row, 1000000l);
+	//From above,we Have assumed that,initially path b/w any two Pair of vertices is Infinite such that Infinite = 1000000l
+	//For simplicity , We can also take path Value = Long.MAX_VALUE , but i have taken Max Value = 1000000l .
+	
+	//Taking Input as Edge Location b/w a pair of vertices
+         for(int i=0;i<m;i++){
+             int x=in.nextInt(),y=in.nextInt();
+             long cmp=in.nextLong();
+             if(w[x][y]>cmp){                      //Comparing previous edge value with current value  -  Cycle Case
+            	w[x][y]=cmp; w[y][x]=cmp;        
+             }
+	}
+	
+	//Implementing Dijkshtra's Algorithm 
+	
+         Stack <Integer> t=new Stack<Integer>();
+          int src=in.nextInt();
+        for(int i=1;i<=n;i++){
+        	if(i!=src){t.push(i);}}
+        Stack <Integer> p=new Stack<Integer>();
+        p.push(src);
+        w[src][src]=0;
+         while(!t.isEmpty()){int min=989997979,loc=-1;
+        for(int i=0;i<t.size();i++){
+        	w[src][t.elementAt(i)]=Math.min(w[src][t.elementAt(i)],w[src][p.peek()]
+                +w[p.peek()][t.elementAt(i)]);
+            if(w[src][t.elementAt(i)]<=min){
+            	min=(int) w[src][t.elementAt(i)];loc=i;}
+        }
+        p.push(t.elementAt(loc));t.removeElementAt(loc);}
+	
+	//Printing shortest path from the given source src
+         for(int i=1;i<=n;i++){
+        	 if(i!=src && w[src][i]!=1000000l){System.out.print(w[src][i]+" ");}
+        	 else if(i!=src){System.out.print("-1"+" ");}    //Printing -1 if there is no path b/w given pair of edges
+         }
+         
+  }
+}