其實我也不太懂矩陣乘法

不過就模擬吧=]

矩陣似乎沒有交換律

/*************************************************************/

#include<stdio.h>
#include<stdlib.h>

main()
{
  int A,B,C,D;
  while(scanf("%d %d %d %d",&A,&B,&C,&D)==4)
       {
            if(B!=C) {printf("Error\n");continue;}
           
            int a,b,c,d;
            int m1[101][101],m2[101][101];
           
            for(a=0;a<A;a++)
               for(b=0;b<B;b++)
                  scanf("%d",&m1[a][b]);
                 
            for(a=0;a<C;a++)
               for(b=0;b<D;b++)
                  scanf("%d",&m2[a][b]);
                 
            int ANS[101][101];
            for(a=0;a<A;a++)
                 for(b=0;b<D;b++)
                    {
                       int SUM=0;
                      
                       for(c=0;c<B;c++)
                          SUM+=m1[a][c]*m2[c][b];
                        ANS[a][b]=SUM;            
                    }
            for(a=0;a<A;a++)
                 {
                 for(b=0;b<D;b++)
                    printf("%d ",ANS[a][b]);
                    printf("\n");
                 }
       }
 return 0;
}