challeng#079, raku solutions

7 files changed, 66 insertions, 14 deletions

diff --git a/challenge-076/feng-chang/raku/ch-1.raku b/challenge-076/feng-chang/raku/ch-1.raku
new file mode 100755
index 0000000000..6b039c80e9
--- /dev/null
+++ b/challenge-076/feng-chang/raku/ch-1.raku
@@ -0,0 +1,13 @@
+#!/bin/env raku
+
+my Int @primes = (2..∞).grep: *.is-prime;
+
+sub sum-of-primes(Int:D $N, Int:D $pi, Int:D $cnt --> Num) {
+    when $N < @primes[$pi]  { Inf }
+    when $N.is-prime        { (1 + $cnt).Num }
+    min(sum-of-primes($N - @primes[$pi], $pi, $cnt + 1),
+        sum-of-primes($N, $pi + 1, $cnt)
+    );
+}
+
+say "$_:\t{sum-of-primes($_, 0, 0)}" for 2..30;
diff --git a/challenge-077/feng-chang/raku/ch-1.raku b/challenge-077/feng-chang/raku/ch-1.raku
index 18676223f9..053b739a43 100755
--- a/challenge-077/feng-chang/raku/ch-1.raku
+++ b/challenge-077/feng-chang/raku/ch-1.raku
@@ -3,26 +3,29 @@
 my Bool $found = False;
 my $Num;
 
+# $N:    = (intial N) - @num.sum
+# @fibs: fibonacci numbers as candidates
+# @num:  solution
 sub fib-sum(Int:D $N, @fibs, @num) {
     if $N == 0 {
         say "{ @num.join(' + ') } = $Num";
         $found = True;
         return;
     }
-    return unless @fibs;
-    return if $N < @fibs[0];
+    return unless @fibs;        # all fibonacci numbers are exhausted
+    return if $N < @fibs[0];    # impossible to find a solution
 
     my @F = @fibs;
     my @N = @num;
     @N.push(@F.shift);
-    fib-sum($N - @fibs[0], @F, @N);
+    fib-sum($N - @fibs[0], @F, @N);     # try all possibilities that includes current candidate
 
-    fib-sum($N, @F, @num);
+    fib-sum($N, @F, @num);              # try all possibilities that excludes current candidate
 }
 
 sub MAIN(Int:D $N) {
     my Int @fibs = 1, 2, * + * ...^ * > $N;
-    $Num = $N;
+    $Num = $N;      # remember the initial N
 
     fib-sum($N, @fibs, Array.new);
     0.say unless $found;
diff --git a/challenge-077/feng-chang/raku/ch-2.raku b/challenge-077/feng-chang/raku/ch-2.raku
index b9fdf10332..04c51308ff 100755
--- a/challenge-077/feng-chang/raku/ch-2.raku
+++ b/challenge-077/feng-chang/raku/ch-2.raku
@@ -1,7 +1,8 @@
 #!/bin/env raku
 
+# read input and surround matrix with O's
+#   e.g.: ./ch-2.raku < data-c2-01.txt
 my @a;
-
 for $*IN.lines -> $line {
     @a.push($line.comb.Array.unshift('O').push('O'));
 }
@@ -11,15 +12,14 @@ my UInt $width = @a[0].elems - 2;
 @a.unshift(['O' xx $width + 2]);;
 @a.push(['O' xx $width + 2]);;
 
+# count lonely X's
 my UInt $cnt = 0;
-for 1..$rows -> $i {
-    for 1..$width -> $j {
-        my $junc = all(@a[$i-1;$j-1], @a[$i-1;$j], @a[$i-1;$j+1],
-                       @a[$i;$j-1],                @a[$i;$j+1],
-                       @a[$i+1;$j-1], @a[$i+1;$j], @a[$i+1;$j+1]
-                   );
-        ++$cnt if @a[$i;$j] eq 'X' and $junc eq 'O';
-    }
+for 1..$rows X 1..$width -> ($i, $j) {
+    my $junc = all(@a[$i-1;$j-1], @a[$i-1;$j], @a[$i-1;$j+1],
+                   @a[$i;$j-1],                @a[$i;$j+1],
+                   @a[$i+1;$j-1], @a[$i+1;$j], @a[$i+1;$j+1]
+               );
+    ++$cnt if @a[$i;$j] eq 'X' and $junc eq 'O';
 }
 
 say $cnt;
diff --git a/challenge-077/feng-chang/raku/data-c2-01.txt b/challenge-077/feng-chang/raku/data-c2-01.txt
new file mode 100644
index 0000000000..32e25b69b9
--- /dev/null
+++ b/challenge-077/feng-chang/raku/data-c2-01.txt
@@ -0,0 +1,3 @@
+OOX
+XOO
+XOO
diff --git a/challenge-077/feng-chang/raku/data-c2-02.txt b/challenge-077/feng-chang/raku/data-c2-02.txt
new file mode 100644
index 0000000000..600d69c9a9
--- /dev/null
+++ b/challenge-077/feng-chang/raku/data-c2-02.txt
@@ -0,0 +1,4 @@
+OOXO
+XOOO
+XOOX
+OXOO
diff --git a/challenge-079/feng-chang/raku/ch-1.raku b/challenge-079/feng-chang/raku/ch-1.raku
new file mode 100755
index 0000000000..e1c93acede
--- /dev/null
+++ b/challenge-079/feng-chang/raku/ch-1.raku
@@ -0,0 +1,6 @@
+#!/bin/env raku
+
+sub MAIN(UInt:D $N) {
+    my UInt $total = (1..$N).map({ $_.base(2).comb.sum }).sum;
+    say "{ $total } % 1000000007 = { $total % 1000000007 }";
+}
diff --git a/challenge-079/feng-chang/raku/ch-2.raku b/challenge-079/feng-chang/raku/ch-2.raku
new file mode 100755
index 0000000000..6bd9822e50
--- /dev/null
+++ b/challenge-079/feng-chang/raku/ch-2.raku
@@ -0,0 +1,23 @@
+#!/bin/env raku
+
+sub trapped-drops(@N) returns UInt {
+    my UInt $cnt;
+
+    repeat {
+        @N.shift while @N.elems > 0 and @N[0]   ≤ 0;
+        @N.pop   while @N.elems > 0 and @N[*-1] ≤ 0;
+        last if @N.elems < 3;
+
+        my $height = min(@N[0, *-1]);
+        for 0..^@N.elems -> $i {
+            my $drop = max(0, $height - @N[$i]);
+            $cnt   += $drop;
+            @N[$i] += $drop - $height;
+        }
+    } while @N.elems > 2;
+
+    $cnt;
+}
+
+say trapped-drops(Array.new(2, 1, 4, 1, 2, 5));
+say trapped-drops(Array.new(3, 1, 3, 1, 1, 5));