001 /*
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004 * Copyright (c) 1997-2010 Oracle and/or its affiliates. All rights reserved.
005 *
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008 * and Distribution License("CDDL") (collectively, the "License"). You
009 * may not use this file except in compliance with the License. You can
010 * obtain a copy of the License at
011 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
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021 * file that accompanied this code.
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023 * Modifications:
024 * If applicable, add the following below the License Header, with the fields
025 * enclosed by brackets [] replaced by your own identifying information:
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039 */
040
041 package com.sun.enterprise.admin.cli;
042
043 public class StringEditDistance {
044
045 /**
046 * Computes the edit distance between two strings.
047 *
048 * <p>
049 * The complexity is O(nm) where n=a.length() and m=b.length().
050 */
051 public static int editDistance(String a, String b) {
052 return new StringEditDistance(a, b).calc();
053 }
054
055 /**
056 * Finds the string in the <code>group</code> closest to
057 * <code>key</code> and returns it.
058 *
059 * @return null if group.length==0.
060 */
061 public static String findNearest(String key, String[] group) {
062 int c = Integer.MAX_VALUE;
063 String r = null;
064 for (int i = 0; i < group.length; i++) {
065 int ed = editDistance(key, group[i]);
066 if (c > ed) {
067 c = ed;
068 r = group[i];
069 }
070 }
071 return r;
072 }
073
074
075 /** cost vector. */
076 private int[] cost;
077
078 /** back buffer. */
079 private int[] back;
080
081 /** Two strings to be compared. */
082 private final String a,b;
083
084 private StringEditDistance(String a, String b) {
085 this.a = a;
086 this.b = b;
087 cost = new int[a.length() + 1];
088 back = new int[a.length() + 1];
089 // back buffer
090 for (int i = 0; i <= a.length(); i++)
091 cost[i] = i;
092 }
093
094 /**
095 * Swaps two buffers.
096 */
097 private void flip() {
098 int[] t = cost;
099 cost = back;
100 back = t;
101 }
102
103 private int min(int a, int b, int c) {
104 return Math.min(a, Math.min(b, c));
105 }
106
107 private int calc() {
108 for (int j = 0; j < b.length(); j++) {
109 flip();
110 cost[0] = j + 1;
111 for (int i = 0; i < a.length(); i++) {
112 int match = (a.charAt(i) == b.charAt(j)) ? 0 : 1;
113 cost[i+1] = min(back[i] + match, cost[i] + 1, back[i+1] + 1);
114 }
115 }
116 return cost[a.length()];
117 }
118 }