Data commit

Task/Run-length-encoding/Fan/run-length-encoding.fan

@@ -0,0 +1,47 @@
+**
+** Generates a run-length encoding for a string
+**
+class RLE
+{
+  Run[] encode(Str s)
+  {
+    runs := Run[,]
+
+    s.size.times |i|
+    {
+      ch := s[i]
+      if (runs.size==0 || runs.last.char != ch)
+        runs.add(Run(ch))
+      runs.last.inc
+    }
+    return runs
+  }
+
+  Str decode(Run[] runs)
+  {
+    buf := StrBuf()
+    runs.each |run|
+    {
+      run.count.times { buf.add(run.char.toChar) }
+    }
+    return buf.toStr
+  }
+
+  Void main()
+  {
+    echo(decode(encode(
+"WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
+        )))
+  }
+
+}
+
+internal class Run
+{
+  Int char
+  Int count := 0
+  new make(Int ch) { char = ch }
+  Void inc() { ++count }
+
+  override Str toStr() { return "${count}${char.toChar}" }
+}