Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
/*
 *  Copyright 2011 Peter Karich 
 * 
 *  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.
 */

public class Main {
    private static int[] longestSubstring(String str1, String str2) {
        if (str1 == null || str1.isEmpty() || str2 == null || str2.isEmpty())
            return null;

        // dynamic programming => save already identical length into array
        // to understand this algo simply print identical length in every entry of the array
        // i+1, j+1 then reuses information from i,j
        // java initializes them already with 0
        int[][] num = new int[str1.length()][str2.length()];
        int maxlen = 0;
        int lastSubstrBegin = 0;
        int endIndex = 0;
        for (int i = 0; i < str1.length(); i++) {
            for (int j = 0; j < str2.length(); j++) {
                if (str1.charAt(i) == str2.charAt(j)) {
                    if ((i == 0) || (j == 0))
                        num[i][j] = 1;
                    else
                        num[i][j] = 1 + num[i - 1][j - 1];

                    if (num[i][j] > maxlen) {
                        maxlen = num[i][j];
                        // generate substring from str1 => i
                        lastSubstrBegin = i - num[i][j] + 1;
                        endIndex = i + 1;
                    }
                }
            }
        }
        return new int[] { lastSubstrBegin, endIndex };
    }
}