Merge pull request #560 from andrezgz/challenge-023

challenge-023 andrezgz solution

2 files changed, 63 insertions, 0 deletions

diff --git a/challenge-023/andrezgz/perl5/ch-1.pl b/challenge-023/andrezgz/perl5/ch-1.pl
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+#!/usr/bin/perl
+
+# https://perlweeklychallenge.org/blog/perl-weekly-challenge-023/
+# Task #1
+# Create a script that prints nth order forward difference series.
+# You should be a able to pass the list of numbers and order number as command line parameters.
+# Let me show you with an example.
+# Suppose we have list (X) of numbers: 5, 9, 2, 8, 1, 6 and we would like to create 1st order forward difference series (Y).
+# So using the formula Y(i) = X(i+1) - X(i), we get the following numbers: (9-5), (2-9), (8-2), (1-8), (6-1).
+# In short, the final series would be: 4, -7, 6, -7, 5. If you noticed, it has one less number than the original series.
+# Similary you can carry on 2nd order forward difference series like: (-7-4), (6+7), (-7-6), (5+7) => -11, 13, -13, 12.
+
+use strict;
+use warnings;
+
+die "Usage: $0 <comma-separated number list> [<order number>]" if @ARGV != 2;
+
+my @list = split /,/,shift;
+die 'List should have at leat 2 numbers' if @list < 2;
+
+my $order = shift || 1;
+die 'Max order is '.$#list if $order > $#list;
+
+for (1 .. $order) {
+    @list = map {$list[$_] - $list[$_-1]} (1 .. $#list);
+    print join(',', @list).$/;
+}
diff --git a/challenge-023/andrezgz/perl5/ch-2.pl b/challenge-023/andrezgz/perl5/ch-2.pl
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+#!/usr/bin/perl
+
+# https://perlweeklychallenge.org/blog/perl-weekly-challenge-023/
+# Task #2
+# Create a script that prints Prime Decomposition of a given number.
+# The prime decomposition of a number is defined as a list of prime numbers which when all multiplied together,
+# are equal to that number. For example, the Prime decomposition of 228 is 2,2,3,19 as 228 = 2 * 2 * 3 * 19.
+
+use strict;
+use warnings;
+
+die "Usage: $0 <number>" if @ARGV == 0;
+my $number = shift;
+
+my @prime_decomp;
+
+foreach my $prime (prime_factors($number)){
+    do {
+        $number /= $prime;
+        push @prime_decomp, $prime;
+    } until ($number % $prime != 0);
+}
+
+print join ',', @prime_decomp;
+
+sub prime_factors {
+    my $n = shift;
+    my @r = grep {$n % $_ == 0 && is_prime($_)} (2 .. $n/2); #get prime divisors
+    return @r ? @r : ($n); # number is prime if no prime divisors were found
+}
+
+sub is_prime {
+    my $n = shift;
+    #every composite number has a prime factor less than or equal to its square root.
+    return 1 == grep {$n % $_ == 0} (1 .. sqrt $n);
+}