CF126B Password

思路：

kmp略作修改。

实现：

 #include <iostream>
 #include <cstdio>
 using namespace std;
 const int MAXN = ;
 int neXt[MAXN];

 void getNext(string s)
 {
     int n = s.length();
     neXt[] = -;
     int k = -, j = ;
     while (j < n)
     {
         if (k == - || s[j] == s[k])
         {
             j++; k++;
             neXt[j] = k;
         }
         else
         {
             k = neXt[k];
         }
     }
 }

 bool kmp(string s, string p)
 {
     int i = , j = ;
     int m = s.length(), n = p.length();
     while (i < m && j < n)
     {
         if (j == - || s[i] == p[j]) i++, j++;
         else j = neXt[j];
     }
     if (j == n) return true;
     return false;
 }

 int main()
 {
     string str;
     cin >> str;
     str += ' ';
     int n = str.length();
     getNext(str);
     int tmp = neXt[n - ];
     bool flg = false;
     while (tmp)
     {
         if (kmp(str.substr(, n - ), str.substr(, tmp)))
         {
             cout << str.substr(, tmp) << endl;
             flg = true;
             break;
         }
         tmp = neXt[tmp];
     }
     if (!flg) cout << "Just a legend" << endl;
     return ;
 }