HDU 4763 求最大长度的串A，使得S满足APAQA

给一个串，让你找一个子串，形如EAEBE，就是一个串在开头结尾中间各出现一次，问这个E最长是多少

Sample Input
5
xy
abc
aaa
aaaaba
aaxoaaaaa

Sample Output
0
0
1
1
2

 # include <cstdio>
 # include <cstring>
 using namespace std;

 char S[] ;
 int next[] ;
 int slen ;
 int tlen ;

 void getNext()
 {
     int j, k;
     j = ; k = -; next[] = -;
     while(j < slen)
         if(k == - || S[j] == S[k])
             next[++j] = ++k;
         else
             k = next[k];

 }

 int main ()
 {
     int T ;
     scanf("%d" , &T);
     while (T--)
     {
         scanf("%s" , S) ;
         slen = strlen(S) ;
         getNext() ;
         int t = slen ;
         int ans =  ;
         while (t > slen/)
            t = next[t] ;
         while(t)
         {
             tlen = t ;
             int i ;
             int flag =  ;

             for(i = t* ; i <= slen - t ; i++)//利用next数组的性质
             {
                 if (next[i] == tlen)
                 {
                     ans = tlen ;
                     flag =  ;
                     break ;
                 }
             }
             if (flag)
                t = next[t] ;
             else
                break ;
         }
         printf("%d\n" , ans) ;

     }

     return  ;
 }

 # include <cstdio>
 # include <cstring>
 using namespace std;

 char S[] ;
 int next[] ;
 int slen ;
 int tlen ;

 void getNext()
 {
     int j, k;
     j = ; k = -; next[] = -;
     while(j < slen)
         if(k == - || S[j] == S[k])
             next[++j] = ++k;
         else
             k = next[k];

 }

 bool kmp(int a , int b)
 {

     int i, j = ;

     for(i = a; i <= b; i++)
     {
         while(j >  && S[i] != S[j])
             j = next[j];
         if(S[i] == S[j])
             j++;
         if(j == tlen)
         {
             return true ;
         }
     }
     return false;
 }

 int main ()
 {
     int T ;
     scanf("%d" , &T);
     while (T--)
     {
         scanf("%s" , S) ;
         slen = strlen(S) ;
         getNext() ;
         int t = slen ;
         int ans =  ;
         while (t > slen/)
            t = next[t] ;
         while(t)
         {
             tlen = t ;
             int flag = kmp(t ,slen - t - ) ;//查看模式串是否匹配主串
             if (flag)
             {
                 ans = t ;
                 break ;
             }
             t = next[t] ;
         }
         printf("%d\n" , ans) ;

     }

     return  ;
 }