Example: Matrix Multiplication in C++

// Matrix Multiplication
#include <iostream>

using namespace std;

// Helper function to print a matrix
void printMatrix(int matrix[][3], int rows, int cols) {
    for (int i = 0; i < rows; ++i) {
        for (int j = 0; j < cols; ++j) {
            cout << matrix[i][j] << " ";
        }
        cout << endl;
    }
}

int main() {
    // For simplicity, we use fixed-size 3x3 matrices in this example.
    // In real applications, consider dynamic allocation or std::vector<std::vector<int>>
    // for matrices of arbitrary sizes.

    // Define two matrices for multiplication
    int matrixA[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };

    int matrixB[3][3] = {
        {9, 8, 7},
        {6, 5, 4},
        {3, 2, 1}
    };

    // Define the result matrix, initialized to zeros
    int resultMatrix[3][3] = {0};

    int rowsA = 3, colsA = 3;
    int rowsB = 3, colsB = 3;

    // Step 1: Check if multiplication is possible
    // The number of columns in the first matrix must equal the number of rows in the second.
    if (colsA != rowsB) {
        cout << "Error: The number of columns in Matrix A (" << colsA << ") must be equal to the number of rows in Matrix B (" << rowsB << ")." << endl;
        cout << "Matrix multiplication is not possible." << endl;
        return 1; // Indicate an error
    }

    cout << "Matrix A:" << endl;
    printMatrix(matrixA, rowsA, colsA);
    cout << endl;

    cout << "Matrix B:" << endl;
    printMatrix(matrixB, rowsB, colsB);
    cout << endl;

    // Step 2: Perform matrix multiplication
    // The resulting matrix will have dimensions rowsA x colsB
    for (int i = 0; i < rowsA; ++i) { // Iterate over rows of the resultMatrix (and matrixA)
        for (int j = 0; j < colsB; ++j) { // Iterate over columns of the resultMatrix (and matrixB)
            for (int k = 0; k < colsA; ++k) { // Iterate over columns of matrixA (and rows of matrixB)
                resultMatrix[i][j] += matrixA[i][k] * matrixB[k][j];
            }
        }
    }

    // Step 3: Display the result matrix
    cout << "Resultant Matrix (A * B):" << endl;
    printMatrix(resultMatrix, rowsA, colsB); // dimensions of result are rowsA x colsB

    return 0;
}