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#!/usr/bin/env perl
use strict;
use warnings;
use feature qw{ say postderef signatures };
no warnings qw{ experimental };
{
say uc 'example 1';
my $nodes;
for my $v (qw( 4 5 6 8 9 )) {
$nodes->{$v} = Node->new($v);
}
$nodes->{8}->left( $nodes->{5} );
$nodes->{8}->right( $nodes->{9} );
$nodes->{5}->left( $nodes->{4} );
$nodes->{5}->right( $nodes->{6} );
say $nodes->{8}->bst();
say '';
}
{
say uc 'example 2';
my $nodes;
for my $v (qw( 3 4 5 6 7 )) {
$nodes->{$v} = Node->new($v);
}
$nodes->{5}->left( $nodes->{4} );
$nodes->{5}->right( $nodes->{7} );
$nodes->{4}->left( $nodes->{3} );
$nodes->{4}->right( $nodes->{6} );
say $nodes->{5}->bst();
say '';
}
package Node;
use List::Util qw{sum0};
sub new ( $class, $value = 0 ) {
my $self = {};
$self->{value} = $value;
$self->{left} = undef;
$self->{right} = undef;
$self->{horizontal} = undef;
$self->{parent} = undef;
return bless $self, $class;
}
# is_bst needs to have either an undefined value,
# indicating non-bst, or an array, to determination
# if the parent node is bst, but that's not the
# output the task needs, so here we massage it into
# place
sub bst ( $self ) {
my $o = $self->is_bst();
return defined $o ? 1 : 0;
}
# if a node is a leaf, it's balanced
# otherwise, we get the values from the left and right
# we then filter them to remove any that would not be
# in that list if the tree wasn't bst
# if the arrays aren't of equal size, return undef
# if the next level of nodes returns undef, return undef
# ultimate output will either be a sorted list of
# values or undef, and that's basically true or false
sub is_bst( $self ) {
if ( $self->is_leaf ) {
my $out = [];
push $out->@*, $self->value;
return $out;
}
my @left;
my @right;
if ( defined $self->left ) {
my $local = $self->left()->is_bst();
return undef if !defined $local;
push @left, $local->@*;
}
if ( defined $self->right ) {
my $local = $self->right()->is_bst();
return undef if !defined $local;
push @right, $local->@*;
}
my @left2 = grep { $_ < $self->value } @left;
my @right2 = grep { $_ > $self->value } @right;
return undef if scalar @left != scalar @left2;
return undef if scalar @right != scalar @right2;
return [ @left, $self->value, @right ];
}
sub distance ( $self ) {
my $d = 0;
my $copy = $self;
while ( !$copy->is_root ) {
$copy = $copy->parent;
$d++;
}
return $d;
}
sub value ( $self, $value = undef ) {
if ( defined $value ) {
$self->{value} = $value;
}
else {
return $self->{value};
}
}
sub is_root ( $self ) {
return defined $self->{parent} ? 0 : 1;
}
sub is_leaf ( $self ) {
return ( !defined $self->{left} && !defined $self->{right} )
? 1
: 0;
}
sub left ( $self, $node = undef ) {
if ( defined $node ) {
$self->{left} = $node;
$node->{parent} = $self;
}
else {
return $self->{left};
}
}
sub right ( $self, $node = undef ) {
if ( defined $node ) {
$self->{right} = $node;
$node->{parent} = $self;
}
else {
return $self->{right};
}
}
sub horizontal ( $self, $node = undef ) {
if ( defined $node ) {
$self->{horizontal} = $node;
$node->{parent} = $self;
}
else {
return $self->{horizontal};
}
}
sub parent ($self ) {
return $self->{parent};
}
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