com.tananaev.jsonpatch.LongestCommonSubsequenceFactory Maven / Gradle / Ivy

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/*
 Copyright 2014 C. A. Fitzgerald

 Licensed 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 com.tananaev.jsonpatch;

import java.util.List;

public class LongestCommonSubsequenceFactory {

    public  List search(List seqA, List seqB) {
        if ( seqA.size() > seqB.size()){
            return subsearch( seqB, seqA );
        } else {
            return subsearch( seqA, seqB );
        }
    }

    private  List subsearch(List shortList, List longList) {
        if ( shortList.isEmpty() ){
            return shortList;
        }

        int delta = longList.size() - shortList.size();

        for( int c = 0; c <= delta; c++ ){
            if ( checkEquals( shortList, longList, c)){
                return shortList;
            }
        }
        //remove one from right
        List rightList = subsearch(shortList.subList(0, shortList.size() - 1), longList);
        //remove one from left
        List leftList = subsearch(shortList.subList(1, shortList.size()), longList);
        if ( leftList.size() > rightList.size() ){
            return leftList;
        } else {
            return rightList;
        }
    }

    private  boolean checkEquals(List shortList, List longList, int index) {
        boolean result = true;
        for ( int c = 0; c < shortList.size();  c++ ){
            result = result && shortList.get(c).equals(longList.get(c+index));
        }
        return result;
    }

    public  int findStartIndex( List sub, List full ){
        for( int c = 0; c < full.size(); c++ ) {
            if (checkEquals(sub, full, c)) {
                return c;
            }
        }
        return -1;
    }

}