/*******************************************************************************
* Copyright 2015-2016 - CNRS (Centre National de Recherche Scientifique)
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*******************************************************************************/
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright 2, 2015nership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package eu.project.ttc.metrics;
public class Levenshtein extends AbstractEditDistance {
private double failThreshold = -1;
@Override
public int compute(String s1, String s2) {
int l = Math.max(s1.length(), s2.length());
int maxDistance = failThreshold == -1 ? Math.min(s1.length(),
s2.length()) : (int) Math.round((1 - failThreshold) * l);
int[][] dp = new int[s1.length() + 1][s2.length() + 1];
for (int i = 0; i < dp.length; i++) {
int bestPossibleEditDistance = dp.length;
for (int j = 0; j < dp[i].length; j++) {
dp[i][j] = i == 0 ? j : j == 0 ? i : 0;
if (i > 0 && j > 0) {
if (s1.charAt(i - 1) == s2.charAt(j - 1)) {
dp[i][j] = dp[i - 1][j - 1];
} else {
dp[i][j] = Math.min(dp[i][j - 1] + 1, Math.min(
dp[i - 1][j - 1] + 1, dp[i - 1][j] + 1));
}
bestPossibleEditDistance = Math.min(
bestPossibleEditDistance, dp[i][j]);
}
}
// After calculating row i, look for the smallest value in a given
// column. Abort is maxDistance is strictly exceeded
if (i > maxDistance && bestPossibleEditDistance > maxDistance) {
return l;
}
}
return dp[s1.length()][s2.length()];
}
@Override
public double normalize(int distance, String source, String target) {
int length = source.length() < target.length() ? target.length()
: source.length();
return 1.0 - ((double) distance / (double) length);
}
@Override
public boolean isFailFast() {
return true;
}
@Override
public void setFailThreshold(double threshold) {
failThreshold = threshold;
}
}