ALGO-60 VIP试题 矩阵乘方

#include<iostream>
#include<string.h>
using namespace std;
const int maxn=2;
int n,m;
struct Matrix{
    int m[maxn][maxn];
    Matrix(){
        memset(m,0,sizeof(m));
    }
};
Matrix Multi(Matrix a,Matrix b){
    Matrix res;
    for(int i=0;i<maxn;i++){
        for(int j=0;j<maxn;j++){
            for(int k=0;k<maxn;k++){
                res.m[i][j] =(res.m[i][j]+a.m[i][k]*b.m[k][j])%m;
            }
        }
    }
    return res;
}
Matrix fastm(Matrix a,int n){
    Matrix res;
    for(int i=0;i<maxn;i++){
        res.m[i][i]=1;
    }
    while(n){
        if(n&1){
            res=Multi(res,a);
        }
        a=Multi(a,a);
        n>>=1;
    }
    return res;
}
int main(){
    cin>>n>>m;
    //看了一下评测记录，单位矩阵对m取余 居然是 0 0 0 0 我傻了，看来得去补补线代了 
    if(n==0){
        for(int i=0;i<maxn;i++){
            for(int j=0;j<maxn;j++){
                cout<<0<<" " ;
            }
            cout<<endl;
        }
        return 0;
    }
    Matrix a;
    for(int i=0;i<maxn;i++){
        for(int j=0;j<maxn;j++){
            cin>>a.m[i][j];
        }
    }
    Matrix res=fastm(a,n);
    for(int i=0;i<maxn;i++){
        for(int j=0;j<maxn;j++){
            cout<<res.m[i][j]<<" ";
        }
        cout<<endl;
    }
    return 0;
}