Data commit

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

@@ -0,0 +1,28 @@
+public class Levenshtein {
+
+    public static int distance(String a, String b) {
+        a = a.toLowerCase();
+        b = b.toLowerCase();
+        // i == 0
+        int [] costs = new int [b.length() + 1];
+        for (int j = 0; j < costs.length; j++)
+            costs[j] = j;
+        for (int i = 1; i <= a.length(); i++) {
+            // j == 0; nw = lev(i - 1, j)
+            costs[0] = i;
+            int nw = i - 1;
+            for (int j = 1; j <= b.length(); j++) {
+                int cj = Math.min(1 + Math.min(costs[j], costs[j - 1]), a.charAt(i - 1) == b.charAt(j - 1) ? nw : nw + 1);
+                nw = costs[j];
+                costs[j] = cj;
+            }
+        }
+        return costs[b.length()];
+    }
+
+    public static void main(String [] args) {
+        String [] data = { "kitten", "sitting", "saturday", "sunday", "rosettacode", "raisethysword" };
+        for (int i = 0; i < data.length; i += 2)
+            System.out.println("distance(" + data[i] + ", " + data[i+1] + ") = " + distance(data[i], data[i+1]));
+    }
+}

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()));
+    }
+}

Task/Levenshtein-distance/Java/levenshtein-distance-3.java

@@ -0,0 +1,73 @@
+import static java.lang.Math.abs;
+import static java.lang.Math.max;
+
+public class Levenshtein {
+
+	public static int ld(String a, String b) {
+		return distance(a, b, -1);
+	}
+	public static boolean ld(String a, String b, int max) {
+		return distance(a, b, max) <= max;
+	}
+	
+	private static int distance(String a, String b, int max) {
+		if (a == b) return 0;
+		int la = a.length();
+		int lb = b.length();
+		if (max >= 0 && abs(la - lb) > max) return max+1;
+		if (la == 0) return lb;
+		if (lb == 0) return la;
+		if (la < lb) {
+			int tl = la; la = lb; lb = tl;
+			String ts = a;  a = b; b = ts;
+		}
+		
+		int[] cost = new int[lb+1];
+		for (int i=0; i<=lb; i+=1) {
+			cost[i] = i;
+		}
+
+		for (int i=1; i<=la; i+=1) {
+			cost[0] = i;
+			int prv = i-1;
+			int min = prv;
+			for (int j=1; j<=lb; j+=1) {
+				int act = prv + (a.charAt(i-1) == b.charAt(j-1) ? 0 : 1);
+				cost[j] = min(1+(prv=cost[j]), 1+cost[j-1], act);
+				if (prv < min) min = prv;
+			}
+			if (max >= 0 && min > max) return max+1;
+		}
+		if (max >= 0 && cost[lb] > max) return max+1;
+		return cost[lb];	
+	}
+	
+	private static int min(int ... a) {
+		int min = Integer.MAX_VALUE;
+		for (int i: a) if (i<min) min = i;
+		return min;
+	}
+	
+	public static void main(String[] args) {
+		System.out.println(
+			ld("kitten","kitten") + " " + // 0
+			ld("kitten","sitten") + " " + // 1
+			ld("kitten","sittes") + " " + // 2
+			ld("kitten","sityteng") + " " + // 3
+			ld("kitten","sittYing") + " " + // 4
+			ld("rosettacode","raisethysword") + " " + // 8
+			ld("kitten","kittenaaaaaaaaaaaaaaaaa") + " " + // 17
+			ld("kittenaaaaaaaaaaaaaaaaa","kitten") // 17
+		);
+		System.out.println(
+			ld("kitten","kitten", 3) + " " + // true
+			ld("kitten","sitten", 3) + " " + // true
+			ld("kitten","sittes", 3) + " " + // true
+			ld("kitten","sityteng", 3) + " " + // true
+			ld("kitten","sittYing", 3) + " " + // false
+			ld("rosettacode","raisethysword", 3) + " " + // false
+			ld("kitten","kittenaaaaaaaaaaaaaaaaa", 3) + " " + // false
+			ld("kittenaaaaaaaaaaaaaaaaa","kitten", 3) // false
+		);
+	}
+}