kmp模板

#include <cstdio>
#include <cstring>
#include <cmath>
#include <queue>
#include <algorithm>
#include <ctype.h>
#include <bitset>
#include <iostream>
#define maxn 100009
#define inf 0x3f3f3f3f
#define mod 1000000007
#define Mat_size 11
using namespace std;
char s[maxn];
int _next[maxn],f[maxn],len;

void getnext()
{
    int j=0,i=_next[0]=-1;
    while(j<len)
    {
        if(i==-1||(s[i]==s[j]))
        {
            i++;
            j++;
            _next[j]=i;
        }
        else
            i=_next[i];
    }
}

int kmp(int l,int r,int t)
{
     int i=0,j=l;
     while(j<=r)
     {
         if(i==-1||s[j]==s[i])
         {
             j++;
             i++;
             if(i==t)
                return 1;
         }
         else
            i=_next[i];
     }
     return 0;
}

int main()
{
   // freopen("d:\\in.txt","r",stdin);
    int cas;
    scanf("%d",&cas);
    while(cas--)
    {
        scanf("%s",s);
        len=strlen(s);
        getnext();
        int k=_next[len];
        while(k)
        {
            if(k<=len/3&&kmp(k,len-k-1,k))
                break;
            k=_next[k];
        }
        printf("%d\n",k);
    }
    return 0;
}