Add tasks for all the new languages

Task/LZW-compression/Swift/lzw-compression.swift

@@ -0,0 +1,62 @@
+class LZW {
+  class func compress(uncompressed:String) -> [Int] {
+    var dict = [String : Int]()
+
+    for i in 0 ..< 256 {
+      let s = String(UnicodeScalar(i))
+      dict[s] = i
+    }
+
+    var dictSize = 256
+    var w = ""
+    var result = [Int]()
+    for c in uncompressed {
+      let wc = w + String(c)
+      if dict[wc] != nil {
+        w = wc
+      } else {
+        result.append(dict[w]!)
+        dict[wc] = dictSize++
+        w = String(c)
+      }
+    }
+
+    if w != "" {
+      result.append(dict[w]!)
+    }
+    return result
+  }
+
+  class func decompress(compressed:[Int]) -> String? {
+    var dict = [Int : String]()
+
+    for i in 0 ..< 256 {
+      dict[i] = String(UnicodeScalar(i))
+    }
+
+    var dictSize = 256
+    var w = String(UnicodeScalar(compressed[0]))
+    var result = w
+    for k in compressed[1 ..< compressed.count] {
+      let entry : String
+      if let x = dict[k] {
+        entry = x
+      } else if k == dictSize {
+        entry = w + String(first(w)!)
+      } else {
+        return nil
+      }
+
+      result += entry
+      dict[dictSize++] = w + String(first(entry)!)
+      w = entry
+    }
+    return result
+  }
+}
+
+let comp = LZW.compress("TOBEORNOTTOBEORTOBEORNOT")
+println(comp)
+if let decomp = LZW.decompress(comp) {
+  println(decomp)
+}