Data commit

Task/Levenshtein-distance-Alignment/Scala/levenshtein-distance-alignment.scala

@@ -0,0 +1,51 @@
+import scala.collection.mutable
+import scala.collection.parallel.ParSeq
+
+object LevenshteinAlignment extends App {
+  val vlad = new Levenshtein("rosettacode", "raisethysword")
+  val alignment = vlad.revLevenstein()
+
+  class Levenshtein(s1: String, s2: String) {
+    val memoizedCosts = mutable.Map[(Int, Int), Int]()
+
+    def revLevenstein(): (String, String) = {
+      def revLev: (Int, Int, String, String) => (String, String) = {
+        case (_, 0, revS1, revS2) => (revS1, revS2)
+        case (0, _, revS1, revS2) => (revS1, revS2)
+        case (i, j, revS1, revS2) =>
+          if (memoizedCosts(i, j) == (memoizedCosts(i - 1, j - 1)
+                                      + (if (s1(i - 1) != s2(j - 1)) 1 else 0)))
+            revLev(i - 1, j - 1, s1(i - 1) + revS1, s2(j - 1) + revS2)
+          else if (memoizedCosts(i, j) == 1 + memoizedCosts(i - 1, j))
+            revLev(i - 1, j, s1(i - 1) + revS1, "-" + revS2)
+          else
+            revLev(i, j - 1, "-" + revS1, s2(j - 1) + revS2)
+      }
+
+      revLev(s1.length, s2.length, "", "")
+    }
+
+    private def levenshtein: Int = {
+      def lev: ((Int, Int)) => Int = {
+        case (k1, k2) =>
+          memoizedCosts.getOrElseUpdate((k1, k2), (k1, k2) match {
+            case (i, 0) => i
+            case (0, j) => j
+            case (i, j) =>
+              ParSeq(1 + lev((i - 1, j)),
+                1 + lev((i, j - 1)),
+                lev((i - 1, j - 1))
+                  + (if (s1(i - 1) != s2(j - 1)) 1 else 0)).min
+          })
+      }
+
+      lev((s1.length, s2.length))
+    }
+
+    levenshtein
+  }
+
+  println(alignment._1)
+  println(alignment._2)
+
+}