## Perl Weekly Challenge 267: Line Count

These are some answers to the Week 267, Task 2, of the Perl Weekly Challenge organized by Mohammad S. Anwar.

Spoiler Alert: This weekly challenge deadline is due in a few days from now (on May 5, 2024 at 23:59). This blog post provides some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.

You are given a string, `\$str`, and a 26-items array `@widths` containing the width of each character from a to z.

Write a script to find out the number of lines and the width of the last line needed to display the given string, assuming you can only fit 100 width units on a line.

Example 1

``````Input: \$str = "abcdefghijklmnopqrstuvwxyz"
@widths = (10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10)
Output: (3, 60)

Line 1: abcdefghij (100 pixels)
Line 2: klmnopqrst (100 pixels)
Line 3: uvwxyz (60 pixels)
``````

Example 2

``````Input: \$str = "bbbcccdddaaa"
@widths = (4,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10)
Output: (2, 4)

Line 1: bbbcccdddaa (98 pixels)
Line 2: a (4 pixels)
``````

### Line Count in Raku

The first step is to build a hash, `%widths`, mapping each letter of the alphabet to its width. Then, we iterate over the letters of the input string: we keep adding letters to the current line so long as the line is not more than 100, or we start a new line.

``````sub line-count(@in_widths, \$in_str) {
my \$i = 0;
my %widths;
for 'a'..'z' -> \$let {
%widths{\$let} = @in_widths[\$i++];
}
my \$line-count = 1;
my \$line-width = 0;
for \$in_str.comb -> \$let {
my \$tmp = \$line-width + %widths{\$let};
if \$tmp <= 100 {
\$line-width = \$tmp;
} else {
\$line-count++;
\$line-width = %widths{\$let};
}
}
return "(\$line-count, \$line-width)";
}

my @tests = (10 xx 26, "abcdefghijklmnopqrstuvwxyz"),
([4,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
10,10,10,10,10,10,10,10,10,10,10], "bbbcccdddaaa");

for @tests -> @test {
printf "%-28s => ", @test[1];
say line-count @test[0], @test[1];
}
``````

This program displays the following output:

``````\$ raku ./line-count.raku
abcdefghijklmnopqrstuvwxyz   => (3, 60)
bbbcccdddaaa                 => (2, 4)
``````

### Line Count in Perl

This is a port to Perl of the above Raku program. We first build a hash to map letters to their width, and then iterate over the letters of the input string to fill lines with length not more than 100.

``````use strict;
use warnings;
use feature 'say';

sub line_count {
my @in_widths = @{\$_[0]};
my \$in_str = \$_[1];
my \$i = 0;
my %widths;
for my \$let ('a'..'z') {
\$widths{\$let} = \$in_widths[\$i++];
}
my \$line_count = 1;
my \$line_width = 0;
for my \$let (split //, \$in_str) {
my \$tmp = \$line_width + \$widths{\$let};
if (\$tmp <= 100) {
\$line_width = \$tmp;
} else {
\$line_count++;
\$line_width = \$widths{\$let};
}
}
return "(\$line_count, \$line_width)";
}

my @tests = ( [[10,10,10,10,10,10,10,10,10,10,10,10,10,10,
10,10,10,10,10,10,10,10,10,10,10,10],
"abcdefghijklmnopqrstuvwxyz"],
[[4,10,10,10,10,10,10,10,10,10,10,10,10,10,
10,10,10,10,10,10,10,10,10,10,10,10],
"bbbcccdddaaa"]);

for my \$test (@tests) {
printf "%-28s => ", \$test->[1];
say line_count \$test->[0], \$test->[1];
}
``````

This program displays the following output:

``````\$ perl ./line_count.pl
abcdefghijklmnopqrstuvwxyz   => (3, 60)
bbbcccdddaaa                 => (2, 4)
``````

## Wrapping up

The next week Perl Weekly Challenge will start soon. If you want to participate in this challenge, please check https://perlweeklychallenge.org/ and make sure you answer the challenge before 23:59 BST (British summer time) on May 12, 2024. And, please, also spread the word about the Perl Weekly Challenge if you can.