Question

  public static <AnyType> void mysteryPrint(BinaryNode<AnyType> t) {
      if( t! = null) {
          System.out.println(t.getElement() );
          mysteryPrint(t.getLeft() );
          System.out.println(t.getElement() );
          mysteryPrint(t.getRight() );
          System.out.println(t.getElement() );
      }
  }

               A
       B               C
           D        E

I have made the tree above and I was wondering whats the easiest was to trace this code find the output?

I am getting ABBDDB so far and I lose track.

Answer 1

Without tracing, it’s relatively straightforward to see what a given tree should print. The structure of the method means that a string will look like this:

<content><left sub-tree><content><right sub-tree><content>

So all you have to do is continually substitute that pattern for the left and right sub-trees (with empty strings for non-existent sub-trees) and get the string.

For your example tree, it looks like this (using [ and ] to show substitutions):

A<left sub-tree>A<right sub-tree>A
A[B<left sub-tree>B<right sub-tree>B]A[C<left sub-tree>C<right sub-tree>C]A
A[B[]B[D<left sub-tree>D<right sub-tree>D]B]A[C[E<left sub-tree>E<right sub-tree>E]C[]C]A
A[B[]B[D[]D[]D]B]A[C[E[]E[]E]C[]C]A

So the method prints out ABBDDDBACEEECCA