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# The Weekly Challenge 200
You can find more information about this weeks, and previous weeks challenges at:
https://theweeklychallenge.org/
If you are not already doing the challenge - it is a good place to practise your
**perl** or **raku**. If it is not **perl** or **raku** you develop in - you can
submit solutions in whichever language you feel comfortable with.
You can find the solutions here on github at:
https://github.com/drbaggy/perlweeklychallenge-club/tree/master/challenge-200/james-smith
# Task 1: Arithmetic Slices
***You are given an array of integers. Write a script to find out all Arithmetic Slices for the given array of integers. An integer array is called arithmetic if it has at least 3 elements and the differences between any three consecutive elements are the same.***
## Solution
There are a number of solutions.. I will start with the first "optimal" one I have... if I have time I'll write up a more compact one.
```perl
sub a_slices {
## Less than 1 value return...
return unless $#_;
## Set start of sequence to 0, d - the difference between entry 1 and entry 0
my($st,$d,@pairs)=(0,$_[1]-$_[0]);
## Loop through all end points
for(my$en=1;$en<@_;$en++) {
## If the gap is different - update gap (and start) and continute through loop
if($_[$en]-$_[$en-1] != $d) {
($st,$d)=($en-1,$_[$en]-$_[$en-1])
## If it is the same add it and all alternative entries
} else {
## We only store the start/end of the runs not the whole sequence
push( @pairs, map { [$_,$en] } $st..$en-2 );
}
}
## Now we find all the start ends and return the series of each of these subsequences.
return [ map { [ @_[ $_->[0] .. $_->[1] ] ] } @pairs ];
}
```
# Task 2: Seven Segment 200
***A seven segment display is an electronic component, usually used to display digits. The segments are labeled 'a' through 'g' as shown: The encoding of each digit can thus be represented compactly as a truth table:***
```
my @truth = qw<abcdef bc abdeg abcdg bcfg acdfg acdefg abc abcdefg abcfg>;
```
***For example, `$truth[1] = ‘bc’`. The digit 1 would have segments ‘b’ and ‘c’ enabled.***
## Solution
```perl
my @truth = qw(abcdef bc abdeg abcdg bcfg acdfg acdefg abc abcdefg abcfg);
my @blank = map { ' ' } 0..6;
## A mapper for segment to what to draw... The rows are represented by pairs of bits 0->blank, 1->LHS, 2->RHS, 3->bar
my %parts = ( 'a' => 0x0003, 'b' => 0x0028, 'c' => 0x0a00, 'd' => 0x3000, 'e' => 0x0500, 'f' => 0x0014, 'g' => 0x00c0, );
## The four "pictures"!
my @parts = ( ' ', '| ', ' |', ' -- ' );
sub display {
## Grab number & initialise output as empty.
my( $n, @out ) = ( shift, map {''} @blank );
while( $n ) {
## Get the last digit & set the display for the digit to blank.
my( $d, @dig ) = ( $n%10, @blank );
## Use our truth table along with part mapping to generate values for each number
for my $bar ( map { $parts{$_} } split //, $truth[$d] ) {
$dig[ $_ ] |= $parts[ $bar&3 ], $bar >>= 2 for 0 .. $#blank
}
## Add to the display...
$out[ $_ ] = $dig[ $_ ].' '.$out[ $_ ] for 0..$#blank;
## Update N...
$n = int( $n / 10 );
}
## Render!
say for @out;
}```
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