Week46.1.raku

#!/usr/bin/perl6
use v6;

use Test;


=begin pod

TASK #1
Cryptic Message
The communication system of an office is broken and message received are not completely reliable. To send message Hello, it ended up sending these following:

H x l 4 !
c e - l o
z e 6 l g
H W l v R
q 9 m # o
Similary another day we received a message repeatedly like below:

P + 2 l ! a t o
1 e 8 0 R $ 4 u
5 - r ] + a > /
P x w l b 3 k \
2 e 3 5 R 8 y u
< ! r ^ ( ) k 0
Write a script to decrypt the above repeated message (one message repeated 6 times).

HINT: Look for characters repeated in a particular position in all six messages received.

=end pod

# ok, it seems that if you look vertically down each column the there are two repeated characters. This marks the first letter (and so on) so message one is "Hello" and 2nd is "PerlRaku"
# so let's write a script for that!
my $message = 'H x l 4 !
c e - l o
z e 6 l g
H W l v R
q 9 m # o';
is unscramble($message),"Hello", "unscrambles ok";
$message='P + 2 l ! a t o
1 e 8 0 R $ 4 u
5 - r ] + a > /
P x w l b 3 k \
2 e 3 5 R 8 y u
< ! r ^ ( ) k 0';
is unscramble($message),"PerlRaku", "unscrambles ok";


sub unscramble($m) {
    my %seen;
    my $unscramble="";
    my @m;
    # make a 2d array
    # split by lines into an array
    # split lines on words (split by spaces) and coerce to a list then push into array 
    for $m.lines {  @m.push( .words.list ) };
    # iterate through the columns using elems of row 0 as limit
    for ^@m[0].elems -> $c {
        my %seen;
        # count the number of seen letters on each row of selected column
        %seen{ @m[$_][$c] }++ for ^@m.elems; 
        # filter the seen hash to get the key value of the item with count 2 and add to unscrambled message
        $unscramble~=%seen.grep( *.value==2)>>.key;
    }
    return $unscramble;
}

Week46.2.raku

#!/usr/bin/perl6
use v6;

use Test;


=begin pod

TASK #2
Is the room open?
There are 500 rooms in a hotel with 500 employees having keys to all the rooms. The first employee opened main entrance door of all the rooms. The second employee then closed the doors of room numbers 2,4,6,8,10 and so on to 500. The third employee then closed the door if it was opened or opened the door if it was closed of rooms 3,6,9,12,15 and so on to 500. Similarly the fourth employee did the same as the third but only room numbers 4,8,12,16 and so on to 500. This goes on until all employees has had a turn.

Write a script to find out all the rooms still open at the end.

=end pod

# initialise doors to open (= 1) after 1st employee opens all doors
my Int @doors = 1 xx 500;
# loop through employees
for 2..500 -> $e {
    my $i=0;
    # iterate through doors
    while $i < 500 {
        @doors[$i] = 1 - @doors[$i];
        $i+=$e;
    }
}
# reduce array by sum of open doors
say @doors.sum;