java最长重复子串

Posted 2022-12-07 快乐崇拜234

正文在下面，先打个广告：

例如：
例如字符串 s =“abcdeabc”
输出：abc

public class Test 
    public static void main(String[] args) 
        System.out.println(maxString("ckabcabck"));
        System.out.println(maxString("abdcdyedhjhyed"));
        System.out.println(maxString("abcdeabc"));
        System.out.println(maxString("ckabcabcl"));

        System.out.println("-----");

        System.out.println(maxString1("ckabcabck"));
        System.out.println(maxString1("abdcdyedhjhyed"));
        System.out.println(maxString1("abcdeabc"));
        System.out.println(maxString1("ckabcabcl"));
    

    //原文：https://blog.csdn.net/qq_14842117/article/details/93887095
    /*
    保存s字符串的所有后缀
对所有后缀进行排序（自然排序）
比较排序后的相邻的后缀的最长公共子串（两个后缀从第一个字符开始的就相等得到公共子串），求出最长的公共子串
*/
    public static String maxString(String s) 
        //保存最长公共子串
        String result = "";
        ArrayList<String> list = new ArrayList<>();
        //得到字符串的所有后缀
        for (int i = s.length() - 1; i >= 0; i--) 
            list.add(s.substring(i));
        
        Collections.sort(list);
        for (int i = 0; i < s.length() - 1; i++) 
            String temp = getComlen(list.get(i), list.get(i + 1));
            if (temp.length() > result.length()) result = temp;
        
        return result;
    

    //得到两个字符串最长公共长度
    public static String getComlen(String str1, String str2) 
        int i;
        for (i = 0; i < str1.length() && i < str2.length(); i++) 
            if (str1.charAt(i) != str2.charAt(i)) 
                break;
            
        

        return  str1.substring(0, i);
    


    //原文：https://wangwenqiang.blog.csdn.net/article/details/95235285?utm_medium=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromBaidu-1.control&depth_1-utm_source=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromBaidu-1.control
    public static String maxString1(String str) 
        if (str == null || str.length() == 0) 
            return "";
        
        //假设重复的字符串相隔1,2,3,4,...str.length();
        int k = 0;
        int max = 0;
        int first = 0;
        for (int i = 1; i < str.length(); i++) 
            //从当前位置开始，将相隔i 的重复的求出来！
            for (int j = 0; j < str.length() - i; j++) 
                if (str.charAt(j) == str.charAt(i + j)) 
                    k++;
                 else 
                    k = 0;
                
                if (k > max) 
                    max = k;
                    first = j - k + 1;//实质为：j-(k-1)
                
            
            k = 0;
        

        return str.substring(first, first + max);