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/*******************************************************************************
*
* Copyright (c) 2004-2011 Oracle Corporation
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Kohsuke Kawaguchi
*
*******************************************************************************/
package hudson.util;
import java.util.Collection;
import java.util.Arrays;
/**
* Computes the string edit distance.
*
* Refer to a computer science text book for the definition of the "string
* edit distance".
*
* @author Kohsuke Kawaguchi ([email protected])
*/
public class EditDistance {
/**
* Computes the edit distance between two strings.
*
*
The complexity is O(nm) where n=a.length() and m=b.length().
*/
public static int editDistance(String a, String b) {
return new EditDistance(a, b).calc();
}
/**
* Finds the string in the
* group closest to
* key and returns it.
*
* @return null if group.length==0.
*/
public static String findNearest(String key, String[] group) {
return findNearest(key, Arrays.asList(group));
}
public static String findNearest(String key, Collection group) {
int c = Integer.MAX_VALUE;
String r = null;
for (String g : group) {
int ed = editDistance(key, g);
if (c > ed) {
c = ed;
r = g;
}
}
return r;
}
/**
* cost vector.
*/
private int[] cost;
/**
* back buffer.
*/
private int[] back;
/**
* Two strings to be compared.
*/
private final String a, b;
private EditDistance(String a, String b) {
this.a = a;
this.b = b;
cost = new int[a.length() + 1];
back = new int[a.length() + 1]; // back buffer
for (int i = 0; i <= a.length(); i++) {
cost[i] = i;
}
}
/**
* Swaps two buffers.
*/
private void flip() {
int[] t = cost;
cost = back;
back = t;
}
private int min(int a, int b, int c) {
return Math.min(a, Math.min(b, c));
}
private int calc() {
for (int j = 0; j < b.length(); j++) {
flip();
cost[0] = j + 1;
for (int i = 0; i < a.length(); i++) {
int match = (a.charAt(i) == b.charAt(j)) ? 0 : 1;
cost[i + 1] = min(back[i] + match, cost[i] + 1, back[i + 1] + 1);
}
}
return cost[a.length()];
}
}