POJ 3233 rapid Matrix Multiplication

I think my professional courses are falling behind, and acm is not doing well in this aspect = It hurts me !! Write a blog and start learning !!

The fast power of the matrix is similar to a ^ B % n. Use the binary idea. In this question, we need to calculate the sum of A + A ^ 2 + A ^ 3 +... + A ^ k. Due to the combination law of matrix multiplication! @ # $ % ^ &*.....

The code is ugly. Take a place... the second write recursion !! My God ~~

#include<iostream>#define MAXN 31using namespace std;struct Matrix{       unsigned long long matrix[MAXN][MAXN];};int n,m;void MatrixPow( int k,Matrix &pre ){     int i,j,p;     if( k<=1 )return ;     else if( k==2 )     {          Matrix now1=pre;         for( i=1;i<=n;i++ )         for( j=1;j<=n;j++ )         {              pre.matrix[i][j]=0;              for( p=1;p<=n;p++ )                   pre.matrix[i][j]+=now1.matrix[i][p]*now1.matrix[p][j];              pre.matrix[i][j]%=m;         }     }     else if( k%2==0 )     {          Matrix now1=pre;          MatrixPow( k>>1,now1 );          MatrixPow( 2,now1 );          pre=now1;     }     else     {         Matrix now1=pre;         Matrix now2=pre;         MatrixPow( k>>1,now1 );         MatrixPow( 2,now1 );         for( i=1;i<=n;i++ )         for( j=1;j<=n;j++ )         {              pre.matrix[i][j]=0;              for( p=1;p<=n;p++ )                   pre.matrix[i][j]+=now1.matrix[i][p]*now2.matrix[p][j];              pre.matrix[i][j]%=m;         }     }}void addMatrix( int k,Matrix &pre ){     int i,j,p;     if( k<=1 )     return ;     else if( k==2 )     {          Matrix now1=pre;          Matrix now2=pre;          MatrixPow( 2,now2 );          for( i=1;i<=n;i++ )          for( j=1;j<=n;j++ )          {               pre.matrix[i][j]=now1.matrix[i][j]+now2.matrix[i][j];               pre.matrix[i][j]%=m;          }     }     else if( k%2==0 )     {          Matrix now1=pre;          Matrix now2=pre;          addMatrix( k>>1,now1 );          MatrixPow( k>>1,now2 );                    for( i=1;i<=n;i++ )          for( j=1;j<=n;j++ )          {               pre.matrix[i][j]=0;               for( p=1;p<=n;p++ )                    pre.matrix[i][j]+=now1.matrix[i][p]*now2.matrix[p][j];               pre.matrix[i][j]%=m;          }                    for( i=1;i<=n;i++ )          for( j=1;j<=n;j++ )          {               pre.matrix[i][j]+=now1.matrix[i][j];               pre.matrix[i][j]%=m;          }     }     else if( k%2==1 )     {         Matrix now1=pre;         Matrix now2=pre;         addMatrix( k-1,now1 );         MatrixPow( k,now2 );         for( i=1;i<=n;i++ )         for( j=1;j<=n;j++ )         {              pre.matrix[i][j]=now1.matrix[i][j]+now2.matrix[i][j];              pre.matrix[i][j]%=m;         }     }}int main(){    int k;    while( scanf( "%d %d %d",&n,&k,&m )!=EOF )    {           int i,j;           Matrix ans;           for( i=1;i<=n;i++ )           for( j=1;j<=n;j++ )           {                scanf( "%llu",&ans.matrix[i][j] );           }           addMatrix( k,ans );                      for( i=1;i<=n;i++ )           {                for( j=1;j<n;j++ )                     printf( "%llu ",ans.matrix[i][j]%m );                printf( "%llu\n",ans.matrix[i][n]%m );                }    }     return 0;}