Data commit

Task/Run-length-encoding/Nim/run-length-encoding.nim

@@ -0,0 +1,36 @@
+import parseutils, strutils
+
+proc compress(input: string): string =
+  var
+    count = 1
+    prev = '\0'
+
+  for ch in input:
+    if ch != prev:
+      if prev != '\0':
+        result.add $count & prev
+      count = 1
+      prev = ch
+    else:
+      inc count
+  result.add $count & prev
+
+proc uncompress(text: string): string =
+  var start = 0
+  var count: int
+  while true:
+    let n = text.parseInt(count, start)
+    if n == 0 or start + n >= text.len:
+      raise newException(ValueError, "corrupted data.")
+    inc start, n
+    result.add repeat(text[start], count)
+    inc start
+    if start == text.len: break
+
+
+const Text = "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
+
+echo "Text:         ", Text
+let compressed = Text.compress()
+echo "Compressed:   ", compressed
+echo "Uncompressed: ", compressed.uncompress()