LZW compression: Difference between revisions

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@@ Line 4,904: / Line 4,904: @@
 {{trans|JavaScript}}
 <lang swift>class LZW {
-  class func compress(uncompressed:String) -> [Int] {
+    class func compress(_ uncompressed:String) -> [Int] {
-    var dict = [String : Int]()
+        var dict = [String : Int]()
-    for i in 0 ..< 256 {
+        for i in 0 ..< 256 {
-      let s = String(UnicodeScalar(i))
+            let s = String(Unicode.Scalar(UInt8(i)))
-      dict[s] = 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 + 1
+                w = String(c)
+            }
+        }
+        if w != "" {
+            result.append(dict[w]!)
+        }
+        return result
     }
+    class func decompress(_ compressed:[Int]) -> String? {
-    var dictSize = 256
-    var w = ""
+        var dict = [Int : String]()
-    var result = [Int]()
-    for c in uncompressed {
+        for i in 0 ..< 256 {
-      let wc = w + String(c)
+            dict[i] = String(Unicode.Scalar(UInt8(i)))
-      if dict[wc] != nil {
+        }
-        w = wc
-      } else {
+        var dictSize = 256
-        result.append(dict[w]!)
+        var w = String(Unicode.Scalar(UInt8(compressed[0])))
-        dict[wc] = dictSize++
+        var result = w
+        for k in compressed[1 ..< compressed.count] {
-        w = String(c)
+            let entry : String
-      }
+            if let x = dict[k] {
+                entry = x
+            } else if k == dictSize {
+                entry = w + String(w[w.startIndex])
+            } else {
+                return nil
+            }
+            result += entry
+            dict[dictSize+1] = w + String(entry[entry.startIndex])
+            w = entry
+        }
+        return result
     }
-    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)
+print(comp)
 if let decomp = LZW.decompress(comp) {
-  println(decomp)
+    print(decomp)
 }</lang>
 {{out}}