luogu3193 [HNOI2008]GT考试

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#include <iostream>
#include <cstdio>
using namespace std;
int n, m, mod, nxt[25], too[25][15];
char ss[25];
struct Matrix{
	int num[25][25];
	Matrix operator*(const Matrix &u)const{
		Matrix re;
		for(int i=0; i<m; i++)
			for(int j=0; j<m; j++){
				re.num[i][j] = 0;
				for(int k=0; k<m; k++)
					re.num[i][j] = (re.num[i][j] + num[i][k]*u.num[k][j]) % mod;
			}
		return re;
	}
}zhu, yua, dan;
void mknxt(){
	int i=0, j;
	j = nxt[0] = -1;
	while(i<m){
		if(j==-1 || ss[i]==ss[j])	nxt[++i] = ++j;
		else	j = nxt[j];
	}
}
void mktoo(){
	for(int i=0; i<m; i++)
		for(int j=0; j<=9; j++){
			too[i][j] = ss[i]==j+'0'?i+1:too[max(nxt[i],0)][j];
			zhu.num[i][too[i][j]]++;
		}
}
int main(){
	cin>>n>>m>>mod;
	scanf("%s", ss);
	mknxt();
	mktoo();
	for(int i=0; i<m; i++)
		dan.num[i][i] = 1;
	yua.num[0][0] = 1;
	while(n){
		if(n&1)	dan = dan * zhu;
		zhu = zhu * zhu;
		n >>= 1;
	}
	yua = yua * dan;
	int ans=0;
	for(int i=0; i<m; i++)
		ans = (ans + yua.num[0][i]) % mod;
	cout<<ans<<endl;
	return 0;
}