#!/usr/local/bin/perl -w
# bintree-traverse.pl -- Traversiert einen binaeren Baum

use strict 'refs';

my $tree = {
    VALUE => '1',
    LEFT  => { VALUE => '2',
               LEFT  => { VALUE => 3 },
               RIGHT => { VALUE => 4 }
             },
    RIGHT => { VALUE => '5',
               LEFT  => { VALUE => 6 },
               RIGHT => { VALUE => 7 }
             }
    };

print "Preorder : "; preorder($tree);  print "\n";
print "Postorder: "; postorder($tree); print "\n";
print "Inorder  : "; inorder($tree);   print "\n";

sub proceed { print "(" . shift() . ")"; }

sub preorder {
    my $root = shift;

    proceed($root->{'VALUE'});
    preorder($root->{'LEFT'})  if exists $root->{'LEFT'};
    preorder($root->{'RIGHT'}) if exists $root->{'RIGHT'};
}

sub postorder {
    my $root = shift;

    postorder($root->{'LEFT'})  if exists $root->{'LEFT'};
    postorder($root->{'RIGHT'}) if exists $root->{'RIGHT'};
    proceed($root->{'VALUE'});
}

sub inorder {
    my $root = shift;

    inorder($root->{'LEFT'})  if exists $root->{'LEFT'};
    proceed($root->{'VALUE'});
    inorder($root->{'RIGHT'}) if exists $root->{'RIGHT'};
}