A-M baby

Task/Levenshtein-distance/Java/levenshtein-distance-1.java

@@ -0,0 +1,40 @@
+public class LevenshteinDistance {
+
+  public static int computeDistance(String s1, String s2) {
+    s1 = s1.toLowerCase();
+    s2 = s2.toLowerCase();
+
+    int[] costs = new int[s2.length() + 1];
+    for (int i = 0; i <= s1.length(); i++) {
+      int lastValue = i;
+      for (int j = 0; j <= s2.length(); j++) {
+        if (i == 0)
+          costs[j] = j;
+        else {
+          if (j > 0) {
+            int newValue = costs[j - 1];
+            if (s1.charAt(i - 1) != s2.charAt(j - 1))
+              newValue = Math.min(Math.min(newValue, lastValue), costs[j]) + 1;
+            costs[j - 1] = lastValue;
+            lastValue = newValue;
+          }
+        }
+      }
+      if (i > 0)
+        costs[s2.length()] = lastValue;
+    }
+    return costs[s2.length()];
+  }
+
+  public static void printDistance(String s1, String s2) {
+    System.out.println(s1 + "-->" + s2 + ": " + computeDistance(s1, s2));
+  }
+
+  public static void main(String[] args) {
+    printDistance("kitten", "sitting");
+    printDistance("rosettacode", "raisethysword");
+    printDistance(new StringBuilder("rosettacode").reverse().toString(), new StringBuilder("raisethysword").reverse().toString());
+    for (int i = 1; i < args.length; i += 2)
+      printDistance(args[i - 1], args[i]);
+  }
+}

Task/Levenshtein-distance/Java/levenshtein-distance-2.java

@@ -0,0 +1,46 @@
+public class Levenshtein{
+    public static int levenshtein(String s, String t){
+        /* if either string is empty, difference is inserting all chars
+         * from the other
+         */
+        if(s.length() == 0) return t.length();
+        if(t.length() == 0) return s.length();
+
+        /* if first letters are the same, the difference is whatever is
+         * required to edit the rest of the strings
+         */
+        if(s.charAt(0) == t.charAt(0))
+            return levenshtein(s.substring(1), t.substring(1));
+
+        /* else try:
+         *      changing first letter of s to that of t,
+         *      remove first letter of s, or
+         *      remove first letter of t
+         */
+        int a = levenshtein(s.substring(1), t.substring(1));
+        int b = levenshtein(s, t.substring(1));
+        int c = levenshtein(s.substring(1), t);
+
+        if(a > b) a = b;
+        if(a > c) a = c;
+
+        //any of which is 1 edit plus editing the rest of the strings
+        return a + 1;
+    }
+
+    public static void main(String[] args) {
+        String s1 = "kitten";
+        String s2 = "sitting";
+        System.out.println("distance between '" + s1 + "' and '"
+                + s2 + "': " + levenshtein(s1, s2));
+        s1 = "rosettacode";
+        s2 = "raisethysword";
+        System.out.println("distance between '" + s1 + "' and '"
+                + s2 + "': " + levenshtein(s1, s2));
+        StringBuilder sb1 = new StringBuilder(s1);
+        StringBuilder sb2 = new StringBuilder(s2);
+        System.out.println("distance between '" + sb1.reverse() + "' and '"
+                + sb2.reverse() + "': "
+                + levenshtein(sb1.reverse().toString(), sb2.reverse().toString()));
+    }
+}