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#! /opt/local/bin/perl
#
# spiral.pl
#
# TASK #2 › Spiral Matrix
# Submitted by: Mohammad S Anwar
# You are given m x n matrix of positive integers.
#
# Write a script to print spiral matrix as list.
#
# Example 1:
# Input:
# [ 1, 2, 3 ]
# [ 4, 5, 6 ]
# [ 7, 8, 9 ]
# Ouput:
# [ 1, 2, 3, 6, 9, 8, 7, 4, 5 ]
#
# Example 2:
# Input:
# [ 1, 2, 3, 4 ]
# [ 5, 6, 7, 8 ]
# [ 9, 10, 11, 12 ]
# [ 13, 14, 15, 16 ]
# Output:
# [ 1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10 ]
#
# 2020 colin crain
## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ##
use warnings;
use strict;
use feature ":5.26";
use POSIX qw( ceil floor );
## ## ## ## ## MAIN:
my $mat;
$mat = [ [1,2,3,4], [5,6,7,8], [9,10,11,12] ];
# $mat = [ [1,2,3], [4,5,6], [7,8,9], [10,11,12], [13,14,15] ];
# $mat = [ [1], [2], [3], [4] ];
# $mat = [ [1,2,3,4] ];
# $mat = [
# [ 1, 2, 3, 4, 5, 6],
# [ 7, 8, 9,10,11,12],
# [13,14,15,16,17,18],
# [19,20,21,22,23,24],
# [25,26,27,28,29,30]
# ];
my @out = spiralize($mat)->@*;
say "@out";
## ## ## ## ## SUBS:
sub spiralize {
my ($mat) = @_;
my $cols = $mat->[0]->@*;
my $rows = $mat->@*;
my $rank = 0; ## loop count of spiral, 0-based
my $out = [];
while (-spiraling) {
## upper - left to right
return $out if $rank > ceil( $rows / 2 - 1);
push $out->@*, $mat->[$rank]->@[$rank..$cols-$rank-1];
## right - top to bottom
return $out if $rank > ceil( $cols / 2 - 1);
for my $row ( $rank+1..$rows-$rank-2 ) {
push $out->@*, $mat->[$row][$cols-$rank-1];
}
## lower - right to left
return $out if $rank > floor( $rows / 2 - 1);
push $out->@*, reverse $mat->[$rows-$rank-1]->@[$rank..$cols-$rank-1] ;
## left - bottom to top
return $out if $rank > floor( $cols / 2 - 1);
for my $row ( reverse $rank+1..$rows-$rank-2 ) {
push $out->@*, $mat->[$row][$rank];
}
$rank++
}
}
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