Develop

BFS.java

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+// Java program to print BFS traversal from a given source vertex. 
+// BFS(int s) traverses vertices reachable from s. 
+import java.io.*; 
+import java.util.*; 
+
+// This class represents a directed graph using adjacency list 
+// representation 
+class Graph 
+{ 
+    private int V;   // No. of vertices 
+    private LinkedList<Integer> adj[]; //Adjacency Lists 
+
+    // Constructor 
+    Graph(int v) 
+    { 
+        V = v; 
+        adj = new LinkedList[v]; 
+        for (int i=0; i<v; ++i) 
+            adj[i] = new LinkedList(); 
+    } 
+
+    // Function to add an edge into the graph 
+    void addEdge(int v,int w) 
+    { 
+        adj[v].add(w); 
+    } 
+
+    // prints BFS traversal from a given source s 
+    void BFS(int s) 
+    { 
+        // Mark all the vertices as not visited(By default 
+        // set as false) 
+        boolean visited[] = new boolean[V]; 
+
+        // Create a queue for BFS 
+        LinkedList<Integer> queue = new LinkedList<Integer>(); 
+
+        // Mark the current node as visited and enqueue it 
+        visited[s]=true; 
+        queue.add(s); 
+
+        while (queue.size() != 0) 
+        { 
+            // Dequeue a vertex from queue and print it 
+            s = queue.poll(); 
+            System.out.print(s+" "); 
+
+            // Get all adjacent vertices of the dequeued vertex s 
+            // If a adjacent has not been visited, then mark it 
+            // visited and enqueue it 
+            Iterator<Integer> i = adj[s].listIterator(); 
+            while (i.hasNext()) 
+            { 
+                int n = i.next(); 
+                if (!visited[n]) 
+                { 
+                    visited[n] = true; 
+                    queue.add(n); 
+                } 
+            } 
+        } 
+    } 
+
+    // Driver method to 
+    public static void main(String args[]) 
+    { 
+        Graph g = new Graph(4); 
+
+        g.addEdge(0, 1); 
+        g.addEdge(0, 2); 
+        g.addEdge(1, 2); 
+        g.addEdge(2, 0); 
+        g.addEdge(2, 3); 
+        g.addEdge(3, 3); 
+
+        System.out.println("Following is Breadth First Traversal "+ 
+                           "(starting from vertex 2)"); 
+
+        g.BFS(2); 
+    } 
+} 

DFS.java

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+// Java program to print DFS traversal from a given given graph 
+import java.io.*; 
+import java.util.*; 
+
+// This class represents a directed graph using adjacency list 
+// representation 
+class Graph 
+{ 
+    private int V;   // No. of vertices 
+
+    // Array  of lists for Adjacency List Representation 
+    private LinkedList<Integer> adj[]; 
+
+    // Constructor 
+    Graph(int v) 
+    { 
+        V = v; 
+        adj = new LinkedList[v]; 
+        for (int i=0; i<v; ++i) 
+            adj[i] = new LinkedList(); 
+    } 
+
+    //Function to add an edge into the graph 
+    void addEdge(int v, int w) 
+    { 
+        adj[v].add(w);  // Add w to v's list. 
+    } 
+
+    // A function used by DFS 
+    void DFSUtil(int v,boolean visited[]) 
+    { 
+        // Mark the current node as visited and print it 
+        visited[v] = true; 
+        System.out.print(v+" "); 
+
+        // Recur for all the vertices adjacent to this vertex 
+        Iterator<Integer> i = adj[v].listIterator(); 
+        while (i.hasNext()) 
+        { 
+            int n = i.next(); 
+            if (!visited[n]) 
+                DFSUtil(n, visited); 
+        } 
+    } 
+
+    // The function to do DFS traversal. It uses recursive DFSUtil() 
+    void DFS(int v) 
+    { 
+        // Mark all the vertices as not visited(set as 
+        // false by default in java) 
+        boolean visited[] = new boolean[V]; 
+
+        // Call the recursive helper function to print DFS traversal 
+        DFSUtil(v, visited); 
+    } 
+
+    public static void main(String args[]) 
+    { 
+        Graph g = new Graph(4); 
+
+        g.addEdge(0, 1); 
+        g.addEdge(0, 2); 
+        g.addEdge(1, 2); 
+        g.addEdge(2, 0); 
+        g.addEdge(2, 3); 
+        g.addEdge(3, 3); 
+
+        System.out.println("Following is Depth First Traversal "+ 
+                           "(starting from vertex 2)"); 
+
+        g.DFS(2); 
+    } 
+} 

Graph.java

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+// A Java Program to detect cycle in an undirected graph 
+import java.io.*; 
+import java.util.*; 
+
+// This class represents a directed graph using adjacency list 
+// representation 
+class Graph 
+{ 
+    private int V;   // No. of vertices 
+    private LinkedList<Integer> adj[]; // Adjacency List Represntation 
+
+    // Constructor 
+    Graph(int v) { 
+        V = v; 
+        adj = new LinkedList[v]; 
+        for(int i=0; i<v; ++i) 
+            adj[i] = new LinkedList(); 
+    } 
+
+    // Function to add an edge into the graph 
+    void addEdge(int v,int w) { 
+        adj[v].add(w); 
+        adj[w].add(v); 
+    } 
+
+    // A recursive function that uses visited[] and parent to detect 
+    // cycle in subgraph reachable from vertex v. 
+    Boolean isCyclicUtil(int v, Boolean visited[], int parent) 
+    { 
+        // Mark the current node as visited 
+        visited[v] = true; 
+        Integer i; 
+
+        // Recur for all the vertices adjacent to this vertex 
+        Iterator<Integer> it = adj[v].iterator(); 
+        while (it.hasNext()) 
+        { 
+            i = it.next(); 
+
+            // If an adjacent is not visited, then recur for that 
+            // adjacent 
+            if (!visited[i]) 
+            { 
+                if (isCyclicUtil(i, visited, v)) 
+                    return true; 
+            } 
+
+            // If an adjacent is visited and not parent of current 
+            // vertex, then there is a cycle. 
+            else if (i != parent) 
+                return true; 
+        } 
+        return false; 
+    } 
+
+    // Returns true if the graph contains a cycle, else false. 
+    Boolean isCyclic() 
+    { 
+        // Mark all the vertices as not visited and not part of 
+        // recursion stack 
+        Boolean visited[] = new Boolean[V]; 
+        for (int i = 0; i < V; i++) 
+            visited[i] = false; 
+
+        // Call the recursive helper function to detect cycle in 
+        // different DFS trees 
+        for (int u = 0; u < V; u++) 
+            if (!visited[u]) // Don't recur for u if already visited 
+                if (isCyclicUtil(u, visited, -1)) 
+                    return true; 
+
+        return false; 
+    } 
+
+
+    // Driver method to test above methods 
+    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(2, 0); 
+        g1.addEdge(0, 3); 
+        g1.addEdge(3, 4); 
+        if (g1.isCyclic()) 
+            System.out.println("Graph contains cycle"); 
+        else
+            System.out.println("Graph doesn't contains cycle"); 
+
+        Graph g2 = new Graph(3); 
+        g2.addEdge(0, 1); 
+        g2.addEdge(1, 2); 
+        if (g2.isCyclic()) 
+            System.out.println("Graph contains cycle"); 
+        else
+            System.out.println("Graph doesn't contains cycle"); 
+    } 
+}