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Matrix using nested for loops in C++

By: Ignatius in C++ Tutorials on 2012年03月16日 [フレーム]

This simple C++ program illustrates the use of three nested for loops. The program multiplies matrix x and y and stores the resulting matrix product xy in matrix z. Both x and y must be compatible for multiplication that means, the number of columns of x must be equal to the number of rows of y.

#include <iostream>
using namespace std;
#define m 3
#define c 2
#define n 4
int main()
{
 int i, j, k;
 // first matrix...
 int x[m][c] = {{1,2},{3,4},{5,6}};
 // second matrix...
 int y[c][n] = {{7,8,9,10},{11,12,13,14}};
 // for storing the matrix product result...
 int z[m][n];
 for(i=0; i<m; i++)
 for(j=0; j<n; j++)
 {
 z[i][j] = 0;
 for(k=0; k<c; k++)
 // same as z[i][j] = z[i][j] + x[i][k] * y[k][j];
 z[i][j] += x[i][k] * y[k][j];
 }
 cout<<"\nMultiply matrix x and matrix y,";
 cout<<"\nThen store the result in matrix z.";
 cout<<"\nMatrix x is 3x2, and matrix y is 2x4,";
 cout<<"\nso, the result, z should be matrix 3x4\n";
 cout<<"\nThe matrix product is: \n";
 for (i=0; i<m; i++)
 {
 cout<<"\n";
 for(j=0; j<n; j++)
 // display the result...
 cout<<" "<<z[i][j];
 }
 cout<<endl;
 return 0;
}

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