7 files changed, 218 insertions, 0 deletions
diff --git a/challenge-175/ulrich-rieke/cpp/ch-2.cpp b/challenge-175/ulrich-rieke/cpp/ch-2.cpp
new file mode 100644
index 0000000000..2f910a3bfc
--- /dev/null
+++ b/challenge-175/ulrich-rieke/cpp/ch-2.cpp
@@ -0,0 +1,55 @@
+#include <iostream>
+#include <vector>
+#include <numeric>
+#include <algorithm>
+
+int my_gcd( int a , int b ) { //Euclid's algorithm
+  if ( b >= a )
+      std::swap( a , b ) ;
+  while ( a != b ) {
+      a = a - b ;
+      if ( b >= a )
+    std::swap( a , b ) ;
+  }
+  return a ;
+}
+
+int myPhi(  int n ) {
+  std::vector<int> totatives ;
+  for ( int i = 1 ; i < n ; i++ ) {
+      if ( my_gcd( i , n ) == 1 )
+    totatives.push_back( i ) ;
+  }
+  return totatives.size( ) ;
+}
+
+bool isPerfectTotient( int n ) {
+  if ( n == 1 ) {
+      return false ;
+  }
+  int current = n ;
+  std::vector<int> totients ;
+  do {
+      current = myPhi( current ) ;
+      totients.push_back( current ) ;
+  } while ( current != 1 ) ;
+  return std::accumulate( totients.begin( ) , totients.end( ) , 0 ) == n ;
+}
+
+int main( ) {
+  std::vector<int> perfectTotients ;
+  int current = 1 ;
+  while ( perfectTotients.size( ) != 20 ) {
+      if ( isPerfectTotient( current ) ) {
+    perfectTotients.push_back( current ) ;
+      }
+      current++ ;
+  }
+  for ( int i : perfectTotients ) {
+      std::cout << i ;
+      if ( i != perfectTotients.back( ) )
+    std::cout << ',' ;
+  }
+  std::cout << std::endl ;
+  return 0 ;
+}
diff --git a/challenge-175/ulrich-rieke/haskell/ch-1.hs b/challenge-175/ulrich-rieke/haskell/ch-1.hs
new file mode 100644
index 0000000000..5175584c08
--- /dev/null
+++ b/challenge-175/ulrich-rieke/haskell/ch-1.hs
@@ -0,0 +1,15 @@
+module Challenge175
+  where
+import Data.Time.Calendar
+
+findLastSunday :: Integer -> Int -> Day
+findLastSunday year month = myFunc $ fromGregorian year month
+(gregorianMonthLength year month )
+  where
+  myFunc :: Day -> Day
+  myFunc d = until ( (== Sunday ) . dayOfWeek ) change d
+    where
+    change = addDays (- 1 )
+
+solution :: Integer -> [String]
+solution year = map (\m -> showGregorian $ findLastSunday year m ) [1 .. 12]
diff --git a/challenge-175/ulrich-rieke/haskell/ch-2.hs b/challenge-175/ulrich-rieke/haskell/ch-2.hs
new file mode 100644
index 0000000000..998bd240a4
--- /dev/null
+++ b/challenge-175/ulrich-rieke/haskell/ch-2.hs
@@ -0,0 +1,14 @@
+module Challenge175_2
+  where
+
+chi :: Int -> Int
+chi n = length $ filter (\i -> gcd i n == 1 ) [1 .. n - 1]
+
+isPerfectTotient :: Int -> Bool
+isPerfectTotient n = (sum $ tail $ until ( (== 1 ) . last ) step [n]) == n
+where
+  step :: [Int] -> [Int]
+  step list = list ++ [ chi $ last list]
+
+solution :: [Int]
+solution = take 20 $ filter isPerfectTotient [1 , 2 ..]
diff --git a/challenge-175/ulrich-rieke/perl/ch-1.pl b/challenge-175/ulrich-rieke/perl/ch-1.pl
new file mode 100644
index 0000000000..408ab32dd9
--- /dev/null
+++ b/challenge-175/ulrich-rieke/perl/ch-1.pl
@@ -0,0 +1,22 @@
+#!/usr/bin/perl ;
+use strict ;
+use warnings ;
+use feature 'say' ;
+use DateTime ;
+
+my $year = $ARGV[0] ;
+my @lastDays = ( 31 , 28 , 31 , 30 , 31 , 30 , 31 , 31 , 30 , 31 , 30 , 31) ;
+my $dt1 = DateTime->new( year => $year , month => 12 , day => 10 ) ;
+if ( $dt1->is_leap_year ) {
+  $lastDays[1] = 29 ;
+}
+my @lastSundays ;
+for my $month( 1 .. 12 ) {
+  my $dt = DateTime->new( year => $year , month => $month , day =>
+    $lastDays[ $month - 1 ] ) ;
+  while ( $dt->day_of_week != 7 ) {
+      $dt->subtract( days => 1 ) ;
+  }
+  push @lastSundays , $dt ;
+}
+map { say $_->ymd} @lastSundays ;
diff --git a/challenge-175/ulrich-rieke/perl/ch-2.pl b/challenge-175/ulrich-rieke/perl/ch-2.pl
new file mode 100644
index 0000000000..15924eaddb
--- /dev/null
+++ b/challenge-175/ulrich-rieke/perl/ch-2.pl
@@ -0,0 +1,65 @@
+#!/usr/bin/perl ;
+use strict ;
+use warnings ;
+use feature 'say' ;
+use List::Util qw ( reduce ) ;
+
+sub gcd { #Euclid's algorithm!
+  my $firstNum = shift ;
+  my $secondNum = shift ;
+  if ( $secondNum >= $firstNum ) {
+      my $swapped = $firstNum ;
+      $firstNum = $secondNum ;
+      $secondNum = $swapped ;
+  }
+  while ( $firstNum != $secondNum ) {
+      $firstNum = $firstNum - $secondNum ;
+      if ( $secondNum >= $firstNum ) {
+    my $swapped = $firstNum ;
+    $firstNum = $secondNum ;
+    $secondNum = $swapped ;
+      }
+  }
+  return $firstNum ;
+}
+
+sub myPhi {
+  my $number = shift ;
+  my @totatives ;
+  for my $i ( 1 .. $number - 1 ) {
+      if ( gcd( $i , $number ) == 1 ) {
+    push @totatives, $i ;
+      }
+  }
+  return scalar( @totatives ) ;
+}
+
+sub isPerfectTotient {
+  my $number = shift ;
+  if ( $number == 1 ) {
+      return 0 ;
+  }
+  my $start = $number ;
+  my @totients ;
+  do {
+      $start = myPhi( $start ) ;
+      push @totients, $start ;
+  } until ( $start == 1 ) ;
+  my $sum = reduce { $a + $b } @totients ;
+  if ( $sum == $number ) {
+      return 1 ;
+  }
+  else {
+      return 0 ;
+  }
+}
+
+my @perfectTotients ;
+my $current = 1 ;
+while ( scalar( @perfectTotients ) != 20 ) {
+  if ( isPerfectTotient( $current ) ) {
+      push @perfectTotients, $current ;
+  }
+  $current++ ;
+}
+say join( ',' , @perfectTotients ) ;
diff --git a/challenge-175/ulrich-rieke/raku/ch-1.raku b/challenge-175/ulrich-rieke/raku/ch-1.raku
new file mode 100644
index 0000000000..42c2278d4a
--- /dev/null
+++ b/challenge-175/ulrich-rieke/raku/ch-1.raku
@@ -0,0 +1,19 @@
+use v6 ;
+
+sub MAIN( Int $year ) {
+  my @lastDays = ( 31 , 28 , 31 , 30 , 31 , 30 , 31 , 31 , 30 , 31 , 30 ,
+    31 ) ;
+  if ( Date.new("$year-01-01").is-leap-year) {
+      @lastDays[ 1 ] = 29 ;
+  }
+  my @lastSundays ;
+  for (1 .. 12 ) -> $month {
+      my $d = Date.new( year => $year , month => $month , day =>
+        @lastDays[ $month - 1 ] ) ;
+      while ( $d.day-of-week != 7 ) {
+    $d = $d.earlier( day => 1 ) ;
+      }
+      @lastSundays.push( $d ) ;
+  }
+  .say for @lastSundays.map( { .Str } ) ;
+}
diff --git a/challenge-175/ulrich-rieke/raku/ch-2.raku b/challenge-175/ulrich-rieke/raku/ch-2.raku
new file mode 100644
index 0000000000..390b1809b3
--- /dev/null
+++ b/challenge-175/ulrich-rieke/raku/ch-2.raku
@@ -0,0 +1,28 @@
+use v6 ;
+
+sub myPhi( Int $n --> Int ) {
+  return (1 .. $n - 1).grep( { $_ gcd $n == 1 }).elems ;
+}
+
+sub isPerfectTotient( Int $n is copy --> Bool ) {
+  if ( $n == 1 ) {
+      return False ;
+  }
+  my @totatives ;
+  my Int $current = $n ;
+  repeat {
+      $current = myPhi( $current ) ;
+      @totatives.push( $current ) ;
+  } until ( $current == 1 ) ;
+  return ([+] @totatives) == $n ;
+}
+
+my @perfectTotients ;
+my Int $current = 1 ;
+while ( @perfectTotients.elems != 20 ) {
+  if ( isPerfectTotient( $current ) ) {
+      @perfectTotients.push( $current ) ;
+  }
+  $current++ ;
+}
+say @perfectTotients ;