Initial data commit

Task/Gray-code/D/gray-code-3.d

@@ -0,0 +1,11 @@
+import std.stdio, std.algorithm, std.range;
+
+string[] g(in uint n) pure nothrow {
+    return n ? g(n - 1).map!q{'0' ~ a}.array ~
+               g(n - 1).retro.map!q{'1' ~ a}.array
+             : [""];
+}
+
+void main() {
+    4.g.writeln;
+}