最长公共子串

package com.example.interview;

import java.util.Scanner;

/**

• 给定两个字符串str1和str2,输出两个字符串的最长公共子串，如果最长公共子串为空，输出-1。

• /
  public class SubString {
  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    while(sc.hasNext()) {
        String str1 = sc.nextLine();
        String str2 = sc.nextLine();
        SubString test = new SubString();
        String r = test.LCS(str1, str2);
        System.out.println(r);
    }
    sc.close();

  }

  public String LCS(String str1, String str2){

    if(str1.length() == 0 || str2.length() == 0){
        return "-1";
    }
    char[] s1 = str1.toCharArray();
    char[] s2 = str2.toCharArray();
    int endIndex = -1;
    int max = 0;
  
    int[][] arr = new int[s1.length][s2.length];
    for (int i = 0; i < s1.length; i++) {
        for (int j = 0; j < s2.length; j++) {
            if(i==0 || j==0) {
                arr[i][j] = s1[i] == s2[j] ? 1: 0;
            } else {
                if(s1[i] == s2[j]) {
                    arr[i][j] = arr[i-1] [j-1] + 1;
                }
  
            }
            if(arr[i][j] > max) {
                max = arr[i][j];
                endIndex = i;
            }
            // System.out.print(arr[i][j]+ " ");
        }
        // System.out.println();
    }
  
    return endIndex==-1 ? "-1" : str1.substring(endIndex-max+1, endIndex+1);

  }
  }