Added Levenshtein Distance class

src/zutil/algo/LevenshteinDistance.java

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2014 ezivkoc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package zutil.algo;
+
+/**
+ * Created by Ziver on 2014-10-07.
+ */
+public class LevenshteinDistance {
+
+    /**
+     * Calculates the Levenshtein Distance(Number of character
+     * changes to equalize the two strings) for two Strings.
+     *
+     * @return The number of changes needed to equalize the two Strings
+     */
+    public static int getDistance(String str1, String str2) {
+        return getDistance(str1, str2,
+                new int[str1.length()+1][str2.length()+1]);
+    }
+
+    /**
+     * Calculates the Levenshtein Distance(Number of character
+     * changes to equalize the two strings) for two Strings.
+     *
+     * @param   matrix  is a int matrix that will be used for the dynamic programing algorithm.
+     *                  NOTE: matrix must be 1 larger than the larges string
+     * @return The number of changes needed to equalize the two Strings
+     */
+    public static int getDistance(String str1, String str2, int[][] matrix) {
+        int len1 = str1.length()+1;
+        int len2 = str2.length()+1;
+        if(matrix.length < len1 || matrix[0].length < len2)
+            throw new IndexOutOfBoundsException("matrix["+matrix.length+"]["+matrix[0].length+"] must be of size ["+len1+"]["+len2+"] or larger");
+
+        // source prefixes can be transformed into empty string by
+        // dropping all characters
+        for (int i = 0; i < len1; i++) {
+            matrix[i][0] = i;
+        }
+        for (int j = 0; j < len2; j++) {
+            matrix[0][j] = j;
+        }
+
+        for (int j=1; j < len2; j++) {
+            for (int i=1; i < len1; i++) {
+                if (str1.charAt(i-1) == str2.charAt(j-1))
+                    matrix[i][j] = matrix[i - 1][j - 1]; // no operation required
+                else {
+                    matrix[i][j] = min(
+                            matrix[i - 1][j] + 1,  // a deletion
+                            matrix[i][j - 1] + 1,  // an insertion
+                            matrix[i - 1][j - 1] + 1); // a substitution
+                }
+            }
+        }
+        /*
+        System.out.println();
+        for (int j=0; j < len2+1; j++) {
+            if(j>1)
+                System.out.print(str2.charAt(j-2)+" ");
+            else
+                System.out.print("_ ");
+            for (int i=0; i < len1+1; i++) {
+                if(j==0) {
+                    if (i > 1)
+                        System.out.print(str1.charAt(i - 2) + " ");
+                    else if (i != 0)
+                        System.out.print("_ ");
+                }
+                else if (i != 0)
+                    System.out.print(matrix[i-1][j-1]+" ");
+            }
+            System.out.println();
+        }
+        System.out.println("\n\n");*/
+        return matrix[len1 - 1][len2 - 1];
+    }
+
+    private static int min(int i, int j, int k){
+        return Math.min(i, Math.min(j, k));
+    }
+}