Java LCS lcs(String a, String b)

Description

lcs

License

Open Source License

Declaration

public static String lcs(String a, String b) 

Method Source Code

//package com.java2s;
/***********************************************************************
 *
 * This software is Copyright (C) 2013 Fabio Corubolo - corubolo@gmail.com - and Meriem Bendis
 * The University of Liverpool/* w  w  w.  jav  a2 s.com*/
 *
 *
 * BranchingStoryGenerator is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * BranchingStoryGenerator is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with JavaFF.  If not, see <http://www.gnu.org/licenses/>.
 *
 ************************************************************************/

public class Main {
    public static String lcs(String a, String b) {
        int[][] lengths = new int[a.length() + 1][b.length() + 1];

        // row 0 and column 0 are initialized to 0 already

        for (int i = 0; i < a.length(); i++)
            for (int j = 0; j < b.length(); j++)
                if (a.charAt(i) == b.charAt(j))
                    lengths[i + 1][j + 1] = lengths[i][j] + 1;
                else
                    lengths[i + 1][j + 1] = Math.max(lengths[i + 1][j], lengths[i][j + 1]);

        // read the substring out from the matrix
        StringBuffer sb = new StringBuffer();
        for (int x = a.length(), y = b.length(); x != 0 && y != 0;) {
            if (lengths[x][y] == lengths[x - 1][y])
                x--;
            else if (lengths[x][y] == lengths[x][y - 1])
                y--;
            else {
                assert a.charAt(x - 1) == b.charAt(y - 1);
                sb.append(a.charAt(x - 1));
                x--;
                y--;
            }
        }

        return sb.reverse().toString();
    }
}

Related

1. lcs(char[] A, char[] B)
2. lcs(char[] inputString1, char[] inputString2, int length1, int length2)
3. LCS(String A, String B)
4. LCS(String a, String b)
5. lcs(String a, String b)
6. lcs(String arg0, String arg1)
7. LCS(String input1, String input2)
8. lcs(String s1, int s1min, int s1max, String s2, int s2min, int s2max)