BZOJ 3670: [Noi2014]动物园 KMP

暴力的做法是求出 $next$ 数组后倍增求解答案.  

但实际上不用这么麻烦，再做一次类似于 KMP 的东西就可以了.         

code: 

#include <bits/stdc++.h> 
#define N 1000006  
#define ll long long 
#define setI(s) freopen(s".in","r",stdin) 
#define setO(s) freopen(s".out","w",stdout) 
using namespace std;  
const ll mod=1000000007;    
int fail[N],num[N];    
char str[N];   
void solve() 
{ 
    scanf("%s",str+1); 
    int n=strlen(str+1);   
    for(int i=1;i<=n;++i) 
        fail[i]=num[i]=0;          
    fail[1]=0,num[1]=1;     
    int pre=0; 
    for(int i=2;i<=n;++i) 
    { 
        for(;pre&&str[pre+1]!=str[i];pre=fail[pre]);        
        if(str[pre+1]==str[i]) 
            ++pre; 
        fail[i]=pre,num[i]=num[pre]+1;     
    }         
    ll ans=1;   
    pre=0;  
    for(int i=1;i<=n;++i) 
    { 
        for(;pre&&str[pre+1]!=str[i];pre=fail[pre]);   
        if(str[pre+1]==str[i])
            ++pre;     
        while(pre&&(pre<<1)>i) 
            pre=fail[pre];      
        ans=ans*(num[pre]+1)%mod; 
    }
    printf("%lld
",ans); 
}
int main() 
{ 
    // setI("input"); 
    int T;  
    scanf("%d",&T); 
    for(int i=1;i<=T;++i) solve(); 
    return 0; 
}