[4293] | 1 | /**
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| 2 | *#########################################################################
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| 3 | *
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| 4 | * A component of the Gatherer application, part of the Greenstone digital
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| 5 | * library suite from the New Zealand Digital Library Project at the
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| 6 | * University of Waikato, New Zealand.
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| 7 | *
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| 8 | * <BR><BR>
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| 9 | *
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| 10 | * Author: John Thompson, Greenstone Digital Library, University of Waikato
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| 11 | *
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| 12 | * <BR><BR>
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| 13 | *
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| 14 | * Copyright (C) 1999 New Zealand Digital Library Project
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| 15 | *
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| 16 | * <BR><BR>
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| 17 | *
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| 18 | * This program is free software; you can redistribute it and/or modify
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| 19 | * it under the terms of the GNU General Public License as published by
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| 20 | * the Free Software Foundation; either version 2 of the License, or
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| 21 | * (at your option) any later version.
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| 22 | *
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| 23 | * <BR><BR>
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| 24 | *
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| 25 | * This program is distributed in the hope that it will be useful,
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| 26 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 27 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 28 | * GNU General Public License for more details.
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| 29 | *
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| 30 | * <BR><BR>
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| 31 | *
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| 32 | * You should have received a copy of the GNU General Public License
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| 33 | * along with this program; if not, write to the Free Software
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| 34 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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| 35 | *########################################################################
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| 36 | */
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| 37 |
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| 38 |
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| 39 |
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| 40 |
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| 41 |
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| 42 |
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| 43 | /* GPL_HEADER */
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| 44 | package org.greenstone.gatherer.util;
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| 45 | /**************************************************************************************
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| 46 | * Title: Gatherer
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| 47 | * Description: The Gatherer: a tool for gathering and enriching a digital collection.
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| 48 | * Company: The University of Waikato
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| 49 | * Written: 28/08/02
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| 50 | * Revised:
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| 51 | * @author John Thompson, 9826509
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| 52 | * @author Michael Gilleland, Merriam Park Software
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| 53 | * @version 2.3
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| 54 | **************************************************************************************/
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| 55 | /** Determines the MED between two metadata element names.<BR>
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| 56 | * Adapted from code by Michael Gilleland, Merriam Park Software, as detailed in a short essay called "Levenshtein Distance, in Three Flavors" available at http://www.merriampark.com/ld.htm.
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| 57 | */
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| 58 | public class MED {
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| 59 | //****************************
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| 60 | // Get minimum of three values
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| 61 | //****************************
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| 62 | static private int Minimum (int a, int b, int c) {
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| 63 | int mi = a;
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| 64 | if (b < mi) {
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| 65 | mi = b;
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| 66 | }
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| 67 | if (c < mi) {
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| 68 | mi = c;
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| 69 | }
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| 70 | return mi;
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| 71 | }
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| 72 | //*****************************
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| 73 | // Compute Levenshtein distance
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| 74 | //*****************************
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| 75 | static public int LD (String s, String t) {
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| 76 | int d[][]; // matrix
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| 77 | int n; // length of s
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| 78 | int m; // length of t
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| 79 | int i; // iterates through s
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| 80 | int j; // iterates through t
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| 81 | char s_i; // ith character of s
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| 82 | char t_j; // jth character of t
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| 83 | int cost; // cost
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| 84 | // Step 1
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| 85 | // Set n to be the length of s.
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| 86 | // Set m to be the length of t.
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| 87 | // If n = 0, return m and exit.
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| 88 | // If m = 0, return n and exit.
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| 89 | // Construct a matrix containing 0..m rows and 0..n columns.
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| 90 | n = s.length ();
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| 91 | m = t.length ();
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| 92 | if (n == 0) {
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| 93 | return m;
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| 94 | }
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| 95 | if (m == 0) {
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| 96 | return n;
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| 97 | }
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| 98 | d = new int[n+1][m+1];
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| 99 | // Step 2
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| 100 | // Initialize the first row to 0..n.
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| 101 | // Initialize the first column to 0..m.
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| 102 | for (i = 0; i <= n; i++) {
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| 103 | d[i][0] = i;
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| 104 | }
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| 105 | for (j = 0; j <= m; j++) {
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| 106 | d[0][j] = j;
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| 107 | }
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| 108 | // Step 3
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| 109 | // Examine each character of s (i from 1 to n).
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| 110 | for (i = 1; i <= n; i++) {
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| 111 | s_i = s.charAt (i - 1);
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| 112 | // Step 4
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| 113 | // Examine each character of t (j from 1 to m).
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| 114 | for (j = 1; j <= m; j++) {
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| 115 | t_j = t.charAt (j - 1);
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| 116 | // Step 5
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| 117 | // If s[i] equals t[j], the cost is 0.
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| 118 | // If s[i] doesn't equal t[j], the cost is 1.
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| 119 | if (s_i == t_j) {
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| 120 | cost = 0;
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| 121 | }
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| 122 | else {
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| 123 | cost = 1;
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| 124 | }
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| 125 | // Step 6
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| 126 | // Set cell d[i,j] of the matrix equal to the minimum of:
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| 127 | // a. The cell immediately above plus 1: d[i-1,j] + 1.
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| 128 | // b. The cell immediately to the left plus 1: d[i,j-1] + 1.
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| 129 | // c. The cell diagonally above and to the left plus the cost: d[i-1,j-1] + cost.
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| 130 | d[i][j] = Minimum (d[i-1][j]+1, d[i][j-1]+1, d[i-1][j-1] + cost);
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| 131 | }
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| 132 | }
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| 133 | // Step 7
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| 134 | // After the iteration steps (3, 4, 5, 6) are complete, the distance is found in cell d[n,m].
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| 135 | int result = d[n][m];
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| 136 | d = null;
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| 137 | return result;
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| 138 | }
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| 139 | }
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