Data update

Task/Move-to-front-algorithm/Crystal/move-to-front-algorithm.cr

@@ -0,0 +1,33 @@
+class Array
+  # useful method to work on parts of the array in-place
+  def slice (start, length)
+    start = size - start if start < 0
+    raise "Out of bounds" unless start >= 0 && length >= 0 && start + length <= size
+    Slice.new(to_unsafe + start, length)
+  end
+end
+
+def encode (message, symbols)
+  symbols = symbols.dup
+  message.chars.map {|ch|
+    idx = symbols.index! ch
+    symbols.slice(0, idx+1).rotate! -1
+    idx
+  }
+end
+
+def decode (message, symbols)
+  symbols = symbols.dup
+  message.map {|idx|
+    ch = symbols[idx]
+    symbols.slice(0, idx+1).rotate! -1
+    ch
+  }.join
+end
+
+symbols = ('a'..'z').to_a
+["broood", "bananaaa", "hiphophiphop"].each do |word|
+  encoded = encode(word, symbols)
+  decoded = decode(encoded, symbols)
+  printf "%-12s -> %-38s -> %s\n", word, encoded, decoded
+end