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|
#!/usr/bin/env perl
use strict;
use warnings;
use feature qw'say state signatures';
no warnings qw'experimental::signatures';
# TASK #1 › Binary Tree Depth
# Submitted by: Mohammad S Anwar
#
# You are given binary tree.
#
# Write a script to find the minimum depth.
#
# The minimum depth is the number of nodes from the root to the nearest leaf node (node without any children).
#
# Example 1:
#
# ```
# Input: '1 | 2 3 | 4 5'
#
# 1
# / \
# 2 3
# / \
# 4 5
#
# Output: 2
# ```
#
#
# ```
# Example 2:
#
# Input: '1 | 2 3 | 4 * * 5 | * 6'
#
# 1
# / \
# 2 3
# / \
# 4 5
# \
# 6
# Output: 3
# ```
run() unless caller();
sub run() {
my ($input) = @ARGV;
my @tokens = tokenize($input);
say minimum_binary_tree_depth(@tokens);
}
sub minimum_binary_tree_depth ( @tokens) {
my $depth = 0;
my $tree = [];
while (@tokens) {
push @$tree, [];
my $num_elems = 2**$depth;
for ( my $i = 0 ; $i < $num_elems ; $i++ ) {
if ( !@tokens || $tokens[0]->isa('SeparatorToken') ) {
## fill row with dummy placeholder tokens.
unshift @tokens,
map { PlaceHolderToken->new(-1) }
0 .. ( $num_elems - 1 - $i ); # Dummy Token
}
my $cur = shift @tokens;
if ( $cur->isa('ValueToken') ) {
if ( $depth && !defined( $tree->[-2][ int( $i / 2 ) ] ) ) {
die join( " ",
"Missing parent for node with value",
$cur->{lexeme},
"at position",
$cur->pos_human_readable(),
"in input\n" );
}
push @{ $tree->[-1] }, $cur->{lexeme};
}
elsif ( $cur->isa('PlaceHolderToken') ) {
if ( $i % 2
&& !defined $tree->[-1][-1]
&& ( !$depth || defined $tree->[-2][ int( $i / 2 ) ] ) )
{
return $depth;
}
push @{ $tree->[-1] }, undef;
## do nothing
}
}
$depth += 1;
# handle optional separatortoken
if ( @tokens && $tokens[0]->isa("SeparatorToken") ) {
shift @tokens;
}
}
return $depth;
}
sub tokenize ( $input) {
my @tokens;
my $pos = 0;
while ( $pos < length $input ) {
my $cur = substr( $input, $pos, 1 );
if ( $cur =~ m/\|/ ) {
push @tokens, SeparatorToken->new($pos);
$pos += 1;
}
elsif ( $cur =~ m/\*/ ) {
push @tokens, PlaceHolderToken->new($pos);
$pos += 1;
}
elsif ( $cur =~ m/\d/ ) {
my $start_pos = $pos;
my $lexeme = '';
do {
$lexeme .= $cur;
$pos += 1;
$cur = substr( $input, $pos, 1 );
} while ( $cur =~ m/\d/ );
push @tokens, ValueToken->new( $lexeme, $pos );
}
elsif ( $cur =~ m/\s/ ) {
do {
$pos += 1;
$cur = substr( $input, $pos, 1 );
} while ( $cur =~ m/\s/ );
}
else {
my $pos_human_readable = $pos + 1;
die "Unexpected input at position $pos_human_readable: '$cur'\n";
}
}
return @tokens;
}
package TokenType {
sub new ( $class, $lexeme, $pos ) {
return bless { lexeme => $lexeme, position => $pos }, $class;
}
sub pos_human_readable($self) {
return $self->{position} + 1;
}
}
package ValueToken {
use base 'TokenType';
}
package PlaceHolderToken {
use base 'TokenType';
sub new ( $class, $pos ) {
return bless { lexeme => '*', position => $pos }, $class;
}
}
package SeparatorToken {
use base 'TokenType';
sub new ( $class, $pos ) {
return bless { lexeme => '|', position => $pos }, $class;
}
}
|
