Perl Weekly Challenge 127: no need for coffee!

One way to let me improve my knowledge about Raku (aka Perl 6) is to implement programs in it. Unluckily, I don’t have any production code to implement in Raku yet (sob!). So, why not try solving the Perl Weekly Challenge tasks?

In the following, the assigned tasks for Challenge 127.

• Task 1
• Task 2

PWC 127 - Task 1

The first task was about finding out if two sets of numbers have intersections. It was easy enough to be solved with a .grep of one set into the other:

sub MAIN() {
    # my @S1 = 1, 2, 5, 3, 4;
    # my @S2 = 4, 6, 7, 8, 9;
    my @S1 = 1, 3, 5, 7, 9;
    my @S2 = 0, 2, 4, 6, 8;

    "0".say and exit if @S1.grep: $_ for @S2;
    "1".say;
}

PWC 127 - Task 2

The second task was about recognizing if a given segment overlaps previous segments. A segment is defined by the start value and the end value.
First of all I created a function is-conflict that accepts two arrays and check if the two are in conflict, that means overlap: if any of them is empty or the value of the second is not within the range of the first, they do not overlaps.

sub is-conflict( @interval-a, @interval-b ) {
    return False if ! @interval-a || ! @interval-b;
    return False if @interval-a ~~ @interval-b;
    return True if @interval-a[ 0 ] <= $_ <= @interval-a[ 1 ] for @interval-b;
    return False;
}

The MAIN is therefore a matter of invoking thwe is-conflict function with every possible array slice for a given position. It is worth noting that I did something more in this task: I countered how many times a segment overlaps, and I did that by using a %conflicts hash that counts how many time the same segment is reported as in conflict. At the end, I print out a result.

sub MAIN() {
    my @intervals = [ [1,4], [3,5], [6,8], [12, 13], [3,20] ];

    my %conflicts;

    for 0 ..^ @intervals.elems -> $i {
        %conflicts{ @intervals[ $i ] }++ if is-conflict( $_, @intervals[ $i ] ) for @intervals[ 0 .. $i - 1 ];
    }

    for %conflicts.kv -> $what, $how-much {
        "$what conflicts $how-much times".say;
    }
}
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The end result of this script is as follows:

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```shell
% raku ch-2.p6
3 20 conflicts 2 times
3 5 conflicts 1 times