depth first search and breadth first search on graph

Question

I am trying to implement a depth first search and breadth first search on a text file. The code is supposed to skip the words in the text file, but perform depth first search and breadth first search on the letters after the words. I am getting an incompatible type error. Below is my code and text file.

prog

           Scanner myScanner = new Scanner(new File(args[0]));
           Graph obj = new Graph();
           while(myScanner.hasNextLine())
           { 
               if(myScanner.hasNext("add"))
               {
                  Node[] n1=new Node[1];
                   Node[] n2=new Node[2];
                   line 23 **obj.add(n1);**
                   obj.add(n2);
                   obj.connectNode(n1,n2);
               }

               if(myScanner.hasNext("breadth"))
               {
                   obj.bfs();
               }

               if(myScanner.hasNext("depth"))
               {
                   obj.dfs();
               }

               if(myScanner.hasNext("remove"))
               {
                   Node[] n1=new Node[1];
                   Node[] n2=new Node[2];
                   obj.remove();
                   obj.remove();
                   obj.connectNode(n1,n2);
               }

            }
        }
}

Graph.java

public class Graph 
{
    public Node rootNode;
    public ArrayList nodes=new ArrayList();
    public int[][] adjMatrix;//Edges will be represented as adjacency Matrix
    int size;
    public void setRootNode(Node n)
    {
        this.rootNode=n;
    }

    public Node getRootNode()
    {
        return this.rootNode;
    }

    public void add(Node n)
    {
        nodes.add(n);
    }


    //This method will be called to make connect two nodes
    public void connectNode(Node start,Node end)
    {
        if(adjMatrix==null)
        {
            size=nodes.size();
            adjMatrix=new int[size][size];
        }

        int startIndex=nodes.indexOf(start);
        int endIndex=nodes.indexOf(end);
        adjMatrix[startIndex][endIndex]=1;
        adjMatrix[endIndex][startIndex]=1;
    }

    private Node getUnvisitedChildNode(Node n)
    {

        int index=nodes.indexOf(n);
        int j=0;
        while(j<size)
        {
            if(adjMatrix[index][j]==1 &&       ((Node)nodes.get(j)).visited==false)
            {
                return (Node)nodes.get(j);
            }
            j++;
        }
        return null;
    }

    //BFS traversal of a tree is performed by the bfs() function
    public void bfs()
    {
        //BFS uses Queue data structure
        Queue q=new LinkedList();
        q.add(this.rootNode);
        printNode(this.rootNode);
        rootNode.visited=true;
        while(!q.isEmpty())
        {
            Node n=(Node)q.remove();
            Node child=null;
            while((child=getUnvisitedChildNode(n))!=null)
            {
                child.visited=true;
                printNode(child);
                q.add(child);
            }
        }
        //Clear visited property of nodes
        remove();
    }

    //DFS traversal of a tree is performed by the dfs() function
    public void dfs()
    {
        //DFS uses Stack data structure
        Stack s=new Stack();
        s.push(this.rootNode);
        rootNode.visited=true;
        printNode(rootNode);
        while(!s.isEmpty())
        {
            Node n=(Node)s.peek();
            Node child=getUnvisitedChildNode(n);
            if(child!=null)
            {
                child.visited=true;
                printNode(child);
                s.push(child);
            }
            else
            {
                s.pop();
            }
        }
        //Clear visited property of nodes
        remove();
    }


    //Utility methods for clearing visited property of node
    void remove()
    {
        int i=0;
        while(i<size)
        {
            Node n=(Node)nodes.get(i);
            n.visited=false;
            i++;
        }
    }

    //Utility methods for printing the node's label
    private void printNode(Node n)
    {
        System.out.print(n.label+" ");
    }

}

Node.java

public class Node 
{
    public char label;
    public boolean visited=false;
    public Node(char l)
    {
        this.label=l;
    }
}

input.txt

add A B
add A C
add B D
add D E
add E A
add E B
breadth A
depth A
remove A B
add B A
breadth B
depth B

Stack trace and line where error occurs? Consider formatting the code and cleaning out the extra space. This makes it easier for others to read. — But I'm Not A Wrapper Class, Apr 28 '16 at 19:45
run: Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - Erroneous sym type: prog2.Graph.add at prog2.Prog2.main(Prog2.java:23) — pinkcouture, Apr 28 '16 at 19:45
We don't know what line 23 is in this case. Also, check [this topic](http://stackoverflow.com/questions/2333285/java-lang-runtimeexception-uncompilable-source-code-what-can-cause-this) out. — But I'm Not A Wrapper Class, Apr 28 '16 at 19:48

score 0 · Answer 1 · answered Apr 28 '16 at 19:48

0

add(Node node) and connectNode(Node start,Node end) receives objects of the class Node not an array [] of Nodes which you're passing here:

                   Node[] n1=new Node[1];
                   Node[] n2=new Node[2];
                   obj.add(n1);
                   obj.add(n2);
                   obj.connectNode(n1,n2);

answered Apr 28 '16 at 19:48

raven

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How would I pass in objects of the class? – pinkcouture Apr 28 '16 at 20:02
What do you want to do? Why are you instantiating an array there in the first place? – raven Apr 28 '16 at 20:03

score 0 · Answer 2 · answered Apr 29 '16 at 03:45

You are doing .add(Node[] nodes) in your line 23, instaed of the required .add(Node node).

You should instantiate new nodes like:

Node node1 = new Node(char1); //some character that you need to pass in according to your code
Node node2 = new Node(char2);
obj.add(node1);
obj.add(node2);
obj.connectNode(node1, node2);

Same goes for remove, don't initialize an array of nodes.

depth first search and breadth first search on graph

2 Answers2