Merge pull request #1488 from fluca1978/pwc54

Pwc54

4 files changed, 112 insertions, 0 deletions

diff --git a/challenge-054/luca-ferrari/blog-1.txt b/challenge-054/luca-ferrari/blog-1.txt
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+https://fluca1978.github.io/2020/03/29/PerlWeeklyChallenge54.html#task1
diff --git a/challenge-054/luca-ferrari/blog-2.txt b/challenge-054/luca-ferrari/blog-2.txt
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+https://fluca1978.github.io/2020/03/29/PerlWeeklyChallenge54.html#task2
diff --git a/challenge-054/luca-ferrari/raku/ch-1.p6 b/challenge-054/luca-ferrari/raku/ch-1.p6
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+#!env rau
+
+# Perl Weekly Challenge 54
+# see <https://perlweeklychallenge.org/blog/perl-weekly-challenge-054/>
+#
+# Task 1
+#
+# kth Permutation Sequence
+# 
+# Write a script to accept two integers n (>=1)
+# and k (>=1). It should print the kth permutation of n integers.
+# For more information, please follow the wiki page.
+# 
+# For example, n=3 and k=4, the possible permutation sequences are listed below:
+#
+# 123
+# 132
+# 213
+# 231
+# 312
+# 321
+# 
+# The script should print the 4th permutation sequence 231.
+
+
+sub MAIN( Int:D :$n where { $n >= 1 },
+        Int:D :$k where { $k >= 1 } ) {
+
+    "Computing the {$k}-th permutation of $n".say;
+
+    # get all the single digits
+    # that can be permutated
+    my @digits;
+    for 1 .. $n {
+        @digits.push: $_;
+    }
+
+
+    my @permutations = @digits.permutations.sort;
+    say "does not exist" if ( $k >= @permutations.elems );
+    say @permutations[ $k - 1 ];
+}
diff --git a/challenge-054/luca-ferrari/raku/ch-2.p6 b/challenge-054/luca-ferrari/raku/ch-2.p6
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+#!env rau
+
+# Perl Weekly Challenge 54
+# see <https://perlweeklychallenge.org/blog/perl-weekly-challenge-054/>
+#
+# Task 2
+#
+# Collatz Conjecture
+#     Contributed by Ryan Thompson
+# 
+# It is thought that the following sequence will always reach 1:
+# 
+#     $n = $n / 2 when $n is even
+#     $n = 3*$n + 1 when $n is odd
+# 
+# For example, if we start at 23, we get the following sequence:
+# 
+#     23 → 70 → 35 → 106 → 53 → 160 → 80 → 40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1
+# 
+# Write a function that finds the Collatz sequence for any positive integer.
+# Notice how the sequence itself may go far above the original starting number.
+#
+#
+# Extra Credit
+# Have your script calculate the sequence length for all starting
+# numbers up to 1000000 (1e6), and output the starting number
+# and sequence length for the longest 20 sequences.
+
+
+
+sub collatz( Int:D $m ) {
+    my @sequence;
+    my $n = $m;
+    while ( $n > 1 ) {
+        if ( $n %% 2 ) {
+            $n /= 2;
+        }
+        else {
+            $n = 3 * $n + 1;    
+        }
+
+        @sequence.push: $n;
+    }
+
+    @sequence;
+}
+
+
+sub MAIN( Int:D $m where { $m > 0 } ) {
+
+    my @sequence = collatz( $m );
+    # print the results
+    @sequence.join( " → " ).say;
+
+
+    # extra credit
+    my %extra;
+    for 1 .. 100000 {
+        %extra{ $_ } = collatz( $_ ).elems;
+    }
+
+    # sort by the length
+    # prints 20 most length sequences data
+    for %extra.sort( { $^b.value <=> $^a.value } )[0..20] -> $p {
+        "Number {$p.key} produces a Collatz sequence of {$p.value} numbers length".say;
+    }
+
+}