From 4d035a0b7a86d4325b6131dc47d04f3875418913 Mon Sep 17 00:00:00 2001
From: Tom Ryder <tom@sanctum.geek.nz>
Date: Sat, 3 Mar 2018 15:14:43 +1300
Subject: Remove an unneeded directory layer

---
 binary-tree.pl | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 binary-tree.pl

(limited to 'binary-tree.pl')

diff --git a/binary-tree.pl b/binary-tree.pl
new file mode 100644
index 0000000..9a23055
--- /dev/null
+++ b/binary-tree.pl
@@ -0,0 +1,79 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use utf8;
+
+use 5.006;
+
+# Start with an empty tree
+my $root = undef;
+
+# Read lines one by one
+while ( defined( my $line = <> ) ) {
+
+    # Create a new node with this line's value, and empty "left" and "right"
+    # references
+    my $new = {
+        line  => $line,
+        left  => undef,
+        right => undef,
+    };
+
+    # If the tree is empty, this can be our first node; skip the rest of this
+    # iteration
+    if ( not defined $root ) {
+        $root = $new;
+        next;
+    }
+
+    # Starting at the root ...
+    my $cur = $root;
+
+    # Until we don't have any more nodes for comparison (i.e. we've found the
+    # place for our new node)...
+    while ( defined $cur ) {
+
+        # Decide whether to add this to the "left" subtree or the "right"
+        # subtree, depending on whether it's less than the current node or not
+        my $dir =
+          $line lt $cur->{line}
+          ? 'left'
+          : 'right';
+
+        # If that reference is undefined, then that's where we'll put this new
+        # node; unset $cur so the loop stops
+        if ( not defined $cur->{$dir} ) {
+            $cur->{$dir} = $new;
+            $cur = undef;
+            next;
+        }
+
+        # Otherwise, we resume descent with the next node
+        $cur = $cur->{$dir};
+    }
+}
+
+# Start a stack of node items to fall back to once we've processed a node, and
+# begin at the root
+my @stack;
+my $cur = $root;
+
+# Keep going as long as there are nodes left in the stack or we have a
+# "current" node to print
+while ( @stack or defined $cur ) {
+
+    # Drill down through the "left" nodes, stacking them up, until we hit NULL
+    while ( defined $cur ) {
+        push @stack, $cur;
+        $cur = $cur->{left};
+    }
+
+    # If there is anything in the stack after doing that, pop off the first
+    # one, print it, and then move to its "right" node
+    if (@stack) {
+        $cur = pop @stack;
+        print "\t$cur->{line}";
+        $cur = $cur->{right};
+    }
+}
-- 
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