Create graphIsTreeOrNot

graphIsTreeOrNot

@@ -0,0 +1,92 @@
+import java.io.*; 
+import java.util.*; 
+
+class Graph 
+{ 
+	private int V; 
+	private LinkedList<Integer> adj[];  
+
+
+	@SuppressWarnings("unchecked")
+	Graph(int v) 
+	{ 
+		V = v; 
+		adj = new LinkedList[V]; 
+		for (int i=0; i<v; ++i) 
+			adj[i] = new LinkedList<Integer>(); 
+	} 
+
+	void addEdge(int v,int w) 
+	{ 
+		adj[v].add(w); 
+		adj[w].add(v); 
+	} 
+
+	boolean isCyclicUtil(int v, boolean visited[], int parent) 
+	{ 
+		// Mark the current node as visited 
+		visited[v] = true; 
+		Integer i; 
+
+		Iterator<Integer> it = adj[v].iterator(); 
+		while (it.hasNext()) 
+		{ 
+			i = it.next(); 
+
+			if (!visited[i]) 
+			{ 
+				if (isCyclicUtil(i, visited, v)) 
+					return true; 
+			} 
+
+			else if (i != parent) 
+			return true; 
+		} 
+		return false; 
+	} 
+
+	// Returns true if the graph is a tree, else false. 
+	boolean isTree() 
+	{ 
+
+		boolean visited[] = new boolean[V]; 
+		for (int i = 0; i < V; i++) 
+			visited[i] = false; 
+		if (isCyclicUtil(0, visited, -1)) 
+			return false; 
+
+		for (int u = 0; u < V; u++) 
+			if (!visited[u]) 
+				return false; 
+
+		return true; 
+	} 
+
+	public static void main(String args[]) 
+	{ 
+		// Create a graph given in the above diagram 
+		Graph g1 = new Graph(5); 
+		g1.addEdge(1, 0); 
+		g1.addEdge(0, 2); 
+		g1.addEdge(0, 3); 
+		g1.addEdge(3, 4); 
+		if (g1.isTree()) 
+			System.out.println("Graph is Tree"); 
+		else
+			System.out.println("Graph is not Tree"); 
+
+		Graph g2 = new Graph(5); 
+		g2.addEdge(1, 0); 
+		g2.addEdge(0, 2); 
+		g2.addEdge(2, 1); 
+		g2.addEdge(0, 3); 
+		g2.addEdge(3, 4); 
+
+		if (g2.isTree()) 
+			System.out.println("Graph is Tree"); 
+		else
+			System.out.println("Graph is not Tree"); 
+
+	} 
+} 
+