Merge pull request #133 from riya24899/master

Added Dijkstra algorithm

Author: Bhrigu Kansra

Graph/Java/dijkstra.java

@@ -0,0 +1,197 @@
+package dijkstra;
+
+import java.io.BufferedReader;
+
+import java.io.IOException;
+
+import java.io.InputStream;
+
+import java.io.InputStreamReader;
+
+import java.util.StringTokenizer;
+
+
+
+/** Class for buffered reading int and double values */
+
+class Reader {
+
+    static BufferedReader reader;
+
+    static StringTokenizer tokenizer;
+
+
+
+    /** call this method to initialize reader for InputStream */
+
+    static void init(InputStream input) {
+
+        reader = new BufferedReader(
+
+                     new InputStreamReader(input) );
+
+        tokenizer = new StringTokenizer("");
+
+    }
+
+
+
+    /** get next word */
+
+    static String next() throws IOException {
+
+        while ( ! tokenizer.hasMoreTokens() ) {
+
+            //TODO add check for eof if necessary
+
+            tokenizer = new StringTokenizer(
+
+                   reader.readLine() );
+
+        }
+
+        return tokenizer.nextToken();
+
+    }
+
+
+
+    static int nextInt() throws IOException {
+
+        return Integer.parseInt( next() );
+
+    }
+
+    static long nextLong() throws IOException {
+
+        return Long.parseLong( next() );
+
+    }
+
+    static double nextDouble() throws IOException {
+
+        return Double.parseDouble( next() );
+
+    }
+
+}
+
+
+class dijkstra {
+
+
+
+	long[][] array;
+
+	long dist[]=new long[11000];
+
+	int parent[]=new int[11000];
+
+	dijkstra (int v) {
+
+		 array=new long[v+1][v+1];
+	}
+
+	void addedge(int src, int dest, long weight) {
+		array[src][dest]=weight;
+		array[dest][src]=weight;
+	}
+	
+
+	int findmin(long [] dist,int size, boolean[] visited) {
+
+		int low=0;
+
+		long min=Integer.MAX_VALUE;
+
+		for (int i=1;i<size;i++) {
+
+			if (dist[i]<min&&visited[i]==false) {
+
+				min=dist[i];
+
+				low=i;
+
+			}
+
+		}
+
+		return low;
+
+	}
+
+	
+
+	int[] DJK(int s){
+
+		
+
+		for (int i=1;i<array.length;i++) {
+
+			dist[i]=Integer.MAX_VALUE;
+
+		}
+
+		dist[s]=0;
+
+		parent[s]=0;
+
+		boolean[] visited=new boolean[array.length];
+
+		for (int i=1;i<array.length;i++) {
+
+			int min=findmin(dist,array.length,visited);
+			visited[min]=true;
+
+			for (int x=1;x<array[min].length;x++) {
+
+				if (array[min][x]!=0 && !visited[x] ) {
+
+					if(array[min][x]<dist[x]) {
+
+						dist[x]=array[min][x];
+						parent[x]=min;
+
+					}
+
+				}
+
+			}
+
+		}
+
+		return parent;
+
+	}
+
+	
+
+	public static void main(String[] args) throws IOException {
+
+		// TODO Auto-generated method stub
+		Reader.init(System.in);
+		int test=Reader.nextInt();
+		for (int t=1;t<=test;t++) {
+			
+			int v=Reader.nextInt();
+			dijkstra obj=new dijkstra(v);
+			int e=Reader.nextInt();
+			long sum=0;
+			for (int x=0;x<e;x++) {
+				int a=Reader.nextInt();
+				int b=Reader.nextInt();
+				long c=Reader.nextLong();
+				sum+=c;
+				obj.addedge(a,b,c);
+			}
+			int[] ans=obj.DJK(1);
+			for(int o=2;o<=v;o++) {
+				sum-=obj.array[o][ans[o]];
+			}
+			System.out.println(sum);
+		}
+			
+	}
+
+}
+