How to perform Matrix multiplication using a 2D Array.

Learn 2D array manipulation and perform Matrix Multiplication in 2D Array. Learn Matrix multiplication by reading this blog, get the Algorithm and the code!

Algorithm

STEP 1: START
STEP 2: IF(COL1 != ROW2) THEN
STEP 3: PRINT('MULTIPLICATION NOT POSSIBLE')
STEP 4: EXIT
STEP 5: ELSE
STEP 6: FOR I=1 TO ROW1 DO
STEP 7: FOR J=1 TO COL2 DO
STEP 8: C[I][J]=0
STEP 9: FOR K=1 TO COL1 DO 
STEP 10: C[I][J]=C[I][J]+(A[I][K]+B[K][J])
STEP 11: ENDFOR
STEP 12: ENDFOR
STEP 13: ENFOR
STEP 14 END

Code

#include <stdio.h>
int a[3][3],b[3][3],c[3][3];
int n;
int input();
int printing();
int multiply();
int transpose();
int sub();
int add();
int main()
{
do{
printf("ENTER 1 for addition 2 for subtraction 3 for 
multiplication 4 for transpose and 0 for exit");
scanf("%d",&n);
switch(n){
case 1:
input();
add();
printf("sum of matrix: \n");
printing();
break;
case 2:
input();
sub();
printing();
break;
case 3:
input();
multiply();
printing();
break;
case 4:
input();
transpose();
printing();
break;
default:
printf("wrong choice");
}
}while(n!=0);
}
int printing(){
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{
printf("%d ",c[i][j]);
}
printf("\n");
}
return 0;
}
int input(){
printf("ENTER THE ELEMENTS");
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{ if(n==4){
printf("a[%d][%d]",i,j);
scanf("%d",&a[i][j]);
}
else{
printf("a[%d][%d]",i,j);
scanf("%d",&a[i][j]);}
printf("b[%d][%d]",i,j);
scanf("%d",&b[i][j]);
}
}
printf("matrix 1 \n");
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{
printf("%d ",a[i][j]);
}
printf("\n");
}
printf("matrix 2 \n");
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{
printf("%d ",b[i][j]);
}
printf("\n");
}
return 0;
}
int add()
{
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{
c[i][j]=a[i][j]+b[i][j];
}
}
return 0;
}
int sub()
{
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{
c[i][j]=a[i][j]-b[i][j];
}
}
return 0;
}
int multiply()
{
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{ c[i][j]=0;
for(int k=0;k<3;k++)
{
c[i][j]=c[i][j]+(a[i][k]*b[k][j]);
}
}
}
return 0; 
}
int transpose(){
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{
c[i][j]=a[j][i];
}
}
return 0;
}

Output

$: ENTER 1 for addition 2 for subtraction 3 for multiplication 4 for 
transpose and 0 for exit3
ENTER THE ELEMENTSa[0][0]3
b[0][0]2
a[0][1]3
b[0][1]4
a[0][2]5
b[0][2]4
a[1][0]3
b[1][0]4
a[1][1]3
b[1][1]4
a[1][2]5
b[1][2]3
a[2][0]4
b[2][0]5
a[2][1]3
4b[2][1]
5
a[2][2]3
b[2][2]4
matrix 1 
3 3 5 
3 3 5 
4 3 3 
matrix 2 
2 4 4 
4 4 3 
5 5 4 
43 49 41 
43 49 41 
35 43 37 
ENTER 1 for addition 2 for subtraction 3 for multiplication 4 for 
transpose and 0 for exit0
wrong choice