Initial data commit

Task/Run-length-encoding/D/run-length-encoding-2.d

@@ -0,0 +1,53 @@
+import std.stdio, std.array, std.conv;
+
+// Similar to the 'look and say' function.
+string encode(in string input) pure nothrow @safe {
+    if (input.empty)
+        return input;
+    char last = input[$ - 1];
+    string output;
+    int count;
+
+    foreach_reverse (immutable c; input) {
+        if (c == last) {
+            count++;
+        } else {
+            output = count.text ~ last ~ output;
+            count = 1;
+            last = c;
+        }
+    }
+
+    return count.text ~ last ~ output;
+}
+
+string decode(in string input) pure /*@safe*/ {
+    string i, result;
+
+    foreach (immutable c; input)
+        switch (c) {
+            case '0': .. case '9':
+                i ~= c;
+                break;
+            case 'A': .. case 'Z':
+                if (i.empty)
+                    throw new Exception("Can not repeat a letter " ~
+                        "without a number of repetitions");
+                result ~= [c].replicate(i.to!int);
+                i.length = 0;
+                break;
+            default:
+                throw new Exception("'" ~ c ~ "' is not alphanumeric");
+        }
+
+    return result;
+}
+
+void main() {
+    immutable txt = "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWW" ~
+                    "WWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW";
+    writeln("Input: ", txt);
+    immutable encoded = txt.encode;
+    writeln("Encoded: ", encoded);
+    assert(txt == encoded.decode);
+}