【jzoj5215】【BZOJ4870】【Shoi2017】【GDOI2018模拟7.9】【组合数问题】【矩阵快速幂】

题目大意

解题思路

暴力60分没毛病。r

code

#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>#define LF double#define LL long long#define ULL unsigned LL#define fo(i,j,k) for(LL i=j;i<=k;i++)#define fd(i,j,k) for(LL i=j;i>=k;i--)#define fr(i,j) for(LL i=begin[j];i;i=next[i])using namespace std;LL max(LL x,LL y){return (x>y)?x:y;}LL min(LL x,LL y){return (x<y)?x:y;}LL const mk=50+9,inf=1e18+7;LL n,p,K,r,ans[mk][mk],mat[mk][mk],tmp[mk][mk];void multansmat(){    fo(i,0,K-1)fo(j,0,K-1)tmp[i][j]=0;    fo(i,0,K-1)fo(j,0,K-1)fo(k,0,K-1)tmp[i][k]=(tmp[i][k]+ans[i][j]*mat[j][k])%p;    fo(i,0,K-1)fo(j,0,K-1)ans[i][j]=tmp[i][j];}void multmatmat(){    fo(i,0,K-1)fo(j,0,K-1)tmp[i][j]=0;    fo(i,0,K-1)fo(j,0,K-1)fo(k,0,K-1)tmp[i][k]=(tmp[i][k]+mat[i][j]*mat[j][k])%p;    fo(i,0,K-1)fo(j,0,K-1)mat[i][j]=tmp[i][j];}int main(){    freopen("d.in","r",stdin);    freopen("d.out","w",stdout);    scanf("%lld%lld%lld%lld",&n,&p,&K,&r);    ans[0][0]=1;    fo(i,0,K-1)mat[i][i]++,mat[i][(i+1==K)?0:i+1]++;    LL nk=n*K;    while(nk){        if(nk&1)multansmat();        multmatmat();        nk>>=1;    }    printf("%lld",ans[0][r]);    return 0;}