题解 | #查找两个字符串a,b中的最长公共子串#，全靠硬编码实现

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNext()) { // 注意 while 处理多个 case
            String str1 = in.next();
            String str2 = in.next();
            char[] chars1 = str1.toCharArray();
            char[] chars2 = str2.toCharArray();
            int length1 = chars1.length;
            int length2 = chars2.length;
            String str = "";
            // 确保拿最小的字符串去对比
            if (length1 <= length2){
                str = getStr(chars1, chars2);
            }else {
                str = getStr(chars2, chars1);
            }
            System.out.println(str);
        }
    }

    public static String getStr(char[] chars1,char[] chars2){
        HashMap<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < chars1.length; i++) {
            char c1 = chars1[i];
            for (int j = 0; j < chars2.length; j++) {
                char c2 = chars2[j];

                if (c2 == c1 ){
                    int count = 1;
                    // 如果两个字符串有一个后面没有元素则不进入循环
                    for (int k = i + 1,z = j + 1; k < chars1.length && z < chars2.length; k++,z++) {
                        if (chars1[k] == chars2[z]){
                            count++;
                            continue;
                        }
                        break;
                    }
                    Integer integer = map.get(i);
                    // 如果有更长的字串，使用长的那个
                    if (integer != null ){
                        int max = Math.max(integer, count);
                        map.put(i,max);
                        continue;
                    }
                    map.put(i,count);
                }
            }
        }
        Set<Map.Entry<Integer, Integer>> entries = map.entrySet();
        int maxValue = 0;
        int index = 0;
        for (Map.Entry<Integer, Integer> entry : entries) {
            Integer value = entry.getValue();
            int max = Math.max(maxValue, value);
            if (max != maxValue){
                maxValue = max;
                index = entry.getKey();
            }
        }
        String s = new String(chars1);
        return s.substring(index,index + maxValue);
    }
}