Question

I’ve been told that the java class TreeMap uses an implementation of a RB tree. If this is the case, how does one do an inorder, preorder and postorder tree-walk on a TreeMap?

Or is this not possible?

Answer 1

You wouldn’t be able to do this with the TreeMap implemented in the Collections library. Here’s an implementation of a Red-Black Tree in Java that you can look at though. Check out the printTree() methods to see how they walk the tree in sorted order.

/**  * Print all items.  */ public void printTree( ) {     printTree( header.right ); }  /**  * Internal method to print a subtree in sorted order.  * @param t the node that roots the tree.  */ private void printTree( RedBlackNode t ) {     if( t != nullNode ) {         printTree( t.left );         System.out.println( t.element );         printTree( t.right );     } } 

From that maybe you can write your own methods to traverse the tree in all three orders.