September Morn Update

Task/Non-continuous-subsequences/C-sharp/non-continuous-subsequences.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+class Program
+{
+    public static void Main() {
+        var sequence = new[] { "A", "B", "C", "D" };
+        foreach (var subset in Subsets(sequence.Length).Where(s => !IsContinuous(s))) {
+            Console.WriteLine(string.Join(" ", subset.Select(i => sequence[i])));
+        }
+    }
+
+    static IEnumerable<List<int>> Subsets(int length) {
+        int[] values = Enumerable.Range(0, length).ToArray();
+        var stack = new Stack<int>(length);
+        for (int i = 0; stack.Count > 0 || i < length; ) {
+            if (i < length) {
+                stack.Push(i++);
+                yield return (from index in stack.Reverse() select values[index]).ToList();
+            } else {
+                i = stack.Pop() + 1;
+                if (stack.Count > 0) i = stack.Pop() + 1;
+            }
+        }
+    }
+
+    static bool IsContinuous(List<int> list) => list[list.Count - 1] - list[0] + 1 == list.Count;
+
+}

Task/Non-continuous-subsequences/Perl/non-continuous-subsequences.pl

@@ -1,6 +1,7 @@
 my ($max, @current);
 sub non_continuous {
-        my ($idx, $has_gap, $found) = @_;
+        my ($idx, $has_gap) = @_;
+        my $found;
 
         for ($idx .. $max) {
                 push @current, $_;
@@ -13,5 +14,5 @@ sub non_continuous {
         $found;
 }
 
-$max = 20;      # 1048365 sequences, 10 seconds-ish
+$max = 20;
 print "found ", non_continuous(1), " sequences\n";