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/*
 * 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.
 */
package org.apache.commons.text.similarity;

/**
 * An edit distance algorithm based on the length of the longest common subsequence between two strings.
 *
 * 

* This code is directly based upon the implementation in {@link LongestCommonSubsequence}. *

* *

* For reference see: * https://en.wikipedia.org/wiki/Longest_common_subsequence_problem. *

* *

For further reading see:

* *

Lothaire, M. Applied combinatorics on words. New York: Cambridge U Press, 2005. 12-13

* * @since 1.0 */ public class LongestCommonSubsequenceDistance implements EditDistance { /** * Object for calculating the longest common subsequence that we can then normalize in apply. */ private final LongestCommonSubsequence longestCommonSubsequence = new LongestCommonSubsequence(); /** * Calculates an edit distance between two CharSequence's left and * right as: left.length() + right.length() - 2 * LCS(left, right), where * LCS is given in {@link LongestCommonSubsequence#apply(CharSequence, CharSequence)}. * * @param left first character sequence * @param right second character sequence * @return distance * @throws IllegalArgumentException * if either String input {@code null} */ @Override public Integer apply(final CharSequence left, final CharSequence right) { // Quick return for invalid inputs if (left == null || right == null) { throw new IllegalArgumentException("Inputs must not be null"); } return left.length() + right.length() - 2 * longestCommonSubsequence.apply(left, right); } }




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