day 7

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/Extensions.cs b/lib/Extensions.cs
new file mode 100644
index 0000000..52863d0
--- /dev/null
+++ b/lib/Extensions.cs
@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace aoc2019.lib
+{
+    public static class Extensions
+    {
+        public static IEnumerable<IEnumerable<T>> Permute<T>(this IEnumerable<T> list)
+        {
+            if (list.Count() == 1) return new[] { list };
+            return list.SelectMany(t => Permute(list.Where(x => !x.Equals(t))), (v, p) => p.Prepend(v));
+        }
+    }
+}