/******************************************************************************
 * Compilation:  javac LongestRepeatedSubstring.java
 * Execution:    java LongestRepeatedSubstring < file.txt
 * Dependencies: StdIn.java SuffixArray.java
 * Data files:   http://algs4.cs.princeton.edu/63suffix/tinyTale.txt
 * http://algs4.cs.princeton.edu/63suffix/mobydick.txt
 *
 * Reads a text string from stdin, replaces all consecutive blocks of
 * whitespace with a single space, and then computes the longest
 * repeated substring in that text using a suffix array.
 *
 * % java LongestRepeatedSubstring < tinyTale.txt
 * 'st of times it was the '
 *
 * % java LongestRepeatedSubstring < mobydick.txt
 * ',- Such a funny, sporty, gamy, jesty, joky, hoky-poky lad, is the Ocean, oh! Th'
 *
 * % java LongestRepeatedSubstring
 * aaaaaaaaa
 * 'aaaaaaaa'
 *
 * % java LongestRepeatedSubstring
 * abcdefg
 * ''
 ******************************************************************************/

package com.brianway.learning.algorithms.algs4utils;

/**
 * The <tt>LongestRepeatedSubstring</tt> class provides a {@link SuffixArray}
 * client for computing the longest repeated substring of a string that
 * appears at least twice. The repeated substrings may overlap (but must
 * be distinct).
 * <p>
 * For additional documentation,
 * see <a href="http://algs4.cs.princeton.edu/63suffix">Section 6.3</a> of
 * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
 * <p>
 * See also {@link LongestCommonSubstring}.
 *
 * @author Robert Sedgewick
 * @author Kevin Wayne
 */
public class LongestRepeatedSubstring {

    // Do not instantiate.
    private LongestRepeatedSubstring() {
    }

    /**
     * Returns the longest common string of the two specified strings.
     *
     * @param  s one string
     * @param  t the other string
     * @return the longest common string that appears as a substring
     */

    /**
     * Returns the longest repeated substring of the specified string.
     *
     * @param text the string
     * @return the longest repeated substring that appears in <tt>text</tt>;
     * the empty string if no such string
     */
    public static String lrs(String text) {
        int N = text.length();
        SuffixArray sa = new SuffixArray(text);
        String lrs = "";
        for (int i = 1; i < N; i++) {
            int length = sa.lcp(i);
            if (length > lrs.length()) {
                // lrs = sa.select(i).substring(0, length);
                lrs = text.substring(sa.index(i), sa.index(i) + length);
            }
        }
        return lrs;
    }

    /**
     * Unit tests the <tt>lrs()</tt> method.
     */
    public static void main(String[] args) {
        String text = StdIn.readAll().replaceAll("\\s+", " ");
        StdOut.println("'" + lrs(text) + "'");
    }
}

/******************************************************************************
 * Copyright 2002-2015, Robert Sedgewick and Kevin Wayne.
 *
 * This file is part of algs4.jar, which accompanies the textbook
 *
 * Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
 * Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
 * http://algs4.cs.princeton.edu
 *
 *
 * algs4.jar 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 3 of the License, or
 * (at your option) any later version.
 *
 * algs4.jar 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 algs4.jar.  If not, see http://www.gnu.org/licenses.
 ******************************************************************************/
