（转载）HDU4565

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4565

这个博客讲的比较好：http://blog.csdn.net/ljd4305/article/details/8987823

题意：给定a,b,,n,m,求Sn

 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include<cmath>
 #include<sstream>
 #include<string>
 using namespace std;
  __int64 b,k,n,mod;
 struct matrix
 {
     __int64 m[][];
 };
 matrix a,per,s,ans;
 void init()//初始化操作
 {
 
     s.m[][]=((*((k%mod)*(k%mod))%mod)%mod+(*b)%mod)%mod;
     s.m[][]=(*(k%mod))%mod;
     s.m[][]=;
     s.m[][]=;
 
     a.m[][]=(*(k%mod))%mod;
     a.m[][]=;
     a.m[][]=(((b%mod)-((k%mod)*(k%mod))%mod)+mod)%mod;
     a.m[][]=;
 }
 matrix mul(matrix x,matrix y)
 {
     matrix temp;
     memset(temp.m,,sizeof(temp.m));
     for(int i=;i<;i++)
         for(int j=;j<;j++)
         for(int k=;k<;k++)
         temp.m[i][j]=(temp.m[i][j]+x.m[i][k]*y.m[k][j])%mod;
     return temp;
 }
 matrix mpow(matrix A,__int64 n)
 {
     matrix B;
     memset(B.m,,sizeof(B.m));
     for(int i=;i<;i++)
         B.m[i][i]=;
     while(n>)
     {
         if(n&)
             B=mul(B,A);
         A=mul(A,A);
         n>>=;
     }
     return B;
 }
 int main()
 {
 
   while(~scanf("%I64d%I64d%I64d%I64d",&k,&b,&n,&mod))
     {
         init();
         if(n==)
         {
             cout<<(*(k%mod))%mod<<endl;
             continue;
         }
         else if(n==)
         {
             cout<<((*(k%mod)*(k%mod))%mod+(*(b%mod))%mod)%mod<<endl;
             continue;
         }
         else
         {
             ans=mpow(a,n-);
             ans=mul(s,ans);
             cout<<ans.m[][]<<endl;
         }
     }
     return ;
 }