bzoj4870: [Shoi2017]组合数问题(DP+矩阵乘法优化)

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio> 
#include<algorithm>
#define ll long long 
#define MOD(x) ((x)>=p?(x)-p:(x))
using namespace std;
const int maxn=310,inf=1e9;
typedef ll mtx[60][60];
int n,p,K,r;
mtx f,g;
void read(int &k)
{
    int f=1;k=0;char c=getchar();
    while(c<‘0‘||c>‘9‘)c==‘-‘&&(f=-1),c=getchar();
    while(c<=‘9‘&&c>=‘0‘)k=k*10+c-‘0‘,c=getchar();
    k*=f;
}
void mul(mtx &a,mtx b)
{
    mtx c;memset(c,0,sizeof(c));
    for(int i=1;i<=K;i++)
    for(int j=1;j<=K;j++)
    for(int k=1;k<=K;k++)
    c[i][j]=(c[i][j]+a[i][k]*b[k][j])%p;
    memcpy(a,c,sizeof(c));
}
void power(ll b)
{
    for(;b;mul(f,f),b>>=1)
    if(b&1)mul(g,f);
}
int main()
{
    read(n);read(p);read(K);read(r);
    for(int i=1;i<=K;i++)g[i][i]=1,f[i][i]=1;
    for(int i=1;i<=K;i++)f[i][(i-2+K)%K+1]++;
    power(1ll*n*K);
    printf("%lld\n",g[r+1][1]);
}