matrix multiplication in c++
#include <iostream>
using namespace std;
int main()
{
int a[10][10], b[10][10], mult[10][10], r1, c1, r2, c2, i, j, k;
cout << "Enter rows and columns for first matrix: ";
cin >> r1 >> c1;
cout << "Enter rows and columns for second matrix: ";
cin >> r2 >> c2;
// If column of first matrix in not equal to row of second matrix,
// ask the user to enter the size of matrix again.
while (c1!=r2)
{
cout << "Error! column of first matrix not equal to row of second.";
cout << "Enter rows and columns for first matrix: ";
cin >> r1 >> c1;
cout << "Enter rows and columns for second matrix: ";
cin >> r2 >> c2;
}
// Storing elements of first matrix.
cout << endl << "Enter elements of matrix 1:" << endl;
for(i = 0; i < r1; ++i)
for(j = 0; j < c1; ++j)
{
cout << "Enter element a" << i + 1 << j + 1 << " : ";
cin >> a[i][j];
}
// Storing elements of second matrix.
cout << endl << "Enter elements of matrix 2:" << endl;
for(i = 0; i < r2; ++i)
for(j = 0; j < c2; ++j)
{
cout << "Enter element b" << i + 1 << j + 1 << " : ";
cin >> b[i][j];
}
// Initializing elements of matrix mult to 0.
for(i = 0; i < r1; ++i)
for(j = 0; j < c2; ++j)
{
mult[i][j]=0;
}
// Multiplying matrix a and b and storing in array mult.
for(i = 0; i < r1; ++i)
for(j = 0; j < c2; ++j)
for(k = 0; k < c1; ++k)
{
mult[i][j] += a[i][k] * b[k][j];
}
// Displaying the multiplication of two matrix.
cout << endl << "Output Matrix: " << endl;
for(i = 0; i < r1; ++i)
for(j = 0; j < c2; ++j)
{
cout << " " << mult[i][j];
if(j == c2-1)
cout << endl;
}
return 0;
}
// C++ program to multiply
// two square matrices.
#include <iostream>
using namespace std;
#define N 4
// This function multiplies
// mat1[][] and mat2[][], and
// stores the result in res[][]
void multiply(int mat1[][N],
int mat2[][N],
int res[][N])
{
int i, j, k;
for (i = 0; i < N; i++) {
for (j = 0; j < N; j++) {
res[i][j] = 0;
for (k = 0; k < N; k++)
res[i][j] += mat1[i][k] * mat2[k][j];
}
}
}
// Driver Code
int main()
{
int i, j;
int res[N][N]; // To store result
int mat1[N][N] = { { 1, 1, 1, 1 },
{ 2, 2, 2, 2 },
{ 3, 3, 3, 3 },
{ 4, 4, 4, 4 } };
int mat2[N][N] = { { 1, 1, 1, 1 },
{ 2, 2, 2, 2 },
{ 3, 3, 3, 3 },
{ 4, 4, 4, 4 } };
multiply(mat1, mat2, res);
cout << "Result matrix is \n";
for (i = 0; i < N; i++) {
for (j = 0; j < N; j++)
cout << res[i][j] << " ";
cout << "\n";
}
return 0;
}
// This code is contributed
// by Soumik Mondal