Binary Tree's

[Bix Beiderbecke]

Help, I'm trying to traverse a Binary Tree in preorder and at the same time writing it to a txt file using FileWriter and PrintWriter, any Ideas?

Thanks

[Kalai Selvan]

hi,

  
   void preorder(TreeNode root) {
   
      if(root != null) {
         //File Operation can be done here....
         preorder(root.left);
         preorder(root.right);
      }
   }

The above function will perform preorder traversing on the tree. It's an recursive function, you have to pass the root node of the tree to the function.

Kalai Selvan T.

[Bix Beiderbecke]

I understand how to do the preorder traversal, the problem is in the actual writing

 private void savePreOrder(BinaryTreeNode t)
{
String outPutFile = "animal.txt";
FileWriter newGame = null;
 
try
{
newGame = new FileWriter(outPutFile);
}
catch(IOException ioe)
{
System.out.println("Could not create the new       file;" + ioe); 
}
PrintWriter write = new PrintWriter(newGame);

if(t != null)
{
write.println(t.data);
preOrder(t.left);
preOrder(t.right);

}
write.close(); 

Maybe this can help someone figure out what i'm doing wrong

[Bix Beiderbecke]

the code should say savePreOrder(t.left) sorry

[Kalai Selvan]

Hi,

  
private void savePreOrder(BinaryTreeNode t) {
  String outPutFile = "animal.txt";
  FileWriter newGame = null;
  try {
    newGame = new FileWriter(outPutFile);
  } catch(IOException ioe) {
    System.out.println("Could not create the new file;" + ioe); 
  }
  PrintWriter write = new PrintWriter(newGame);
  preOrder(root, write); //Where root is the root node of  the tree.
  writer.close();
}
 
void preorder(TreeNode root, PrintWriter writer) {
  if(root != null) {
    writer.println(root.data);   
    preorder(root.left);         
    preorder(root.right);      
  }   
}
 

I hope the code fragment will solve ur problem.....

Kalai Selvan T.

[Julian Kennedy]

For the uninitiated, the answer was (as nicely demonstrated by Kalai Selvan T's example) that the output file was being recreated every time savePreOrder() was called (i.e. for each node in the tree). The resulting output file would simply have contained the data for a single tree node.

I'd better be right about that now!

Jules