Example: Matrix Addition Using Pointers in C

// Matrix Addition Using Pointers
#include <stdio.h>
#include <stdlib.h> // For malloc and free

// Function to dynamically allocate a matrix
int** allocateMatrix(int rows, int cols) {
    int** matrix = (int**)malloc(rows * sizeof(int*));
    if (matrix == NULL) {
        perror("Memory allocation failed for rows");
        exit(EXIT_FAILURE);
    }
    for (int i = 0; i < rows; i++) {
        matrix[i] = (int*)malloc(cols * sizeof(int));
        if (matrix[i] == NULL) {
            perror("Memory allocation failed for columns");
            // Free previously allocated rows before exiting
            for (int j = 0; j < i; j++) {
                free(matrix[j]);
            }
            free(matrix);
            exit(EXIT_FAILURE);
        }
    }
    return matrix;
}

// Function to read elements into a matrix
void readMatrix(int** matrix, int rows, int cols) {
    printf("Enter elements:\n");
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("Enter element [%d][%d]: ", i, j);
            scanf("%d", &matrix[i][j]);
        }
    }
}

// Function to add two matrices using pointers
void addMatrices(int** mat1, int** mat2, int** result, int rows, int cols) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            // Accessing elements using array-like indexing on pointers
            result[i][j] = mat1[i][j] + mat2[i][j];
            // Alternative using pointer arithmetic:
            // *(*(result + i) + j) = *(*(mat1 + i) + j) + *(*(mat2 + i) + j);
        }
    }
}

// Function to print a matrix
void printMatrix(int** matrix, int rows, int cols) {
    printf("Matrix:\n");
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("%d\t", matrix[i][j]);
        }
        printf("\n");
    }
}

// Function to free dynamically allocated matrix memory
void freeMatrix(int** matrix, int rows) {
    if (matrix == NULL) return;
    for (int i = 0; i < rows; i++) {
        free(matrix[i]); // Free each row
    }
    free(matrix); // Free the array of row pointers
}

int main() {
    int rows, cols;

    // Step 1: Get dimensions from the user
    printf("Enter number of rows: ");
    scanf("%d", &rows);
    printf("Enter number of columns: ");
    scanf("%d", &cols);

    // Step 2: Dynamically allocate memory for the two input matrices and the result matrix
    int** matrixA = allocateMatrix(rows, cols);
    int** matrixB = allocateMatrix(rows, cols);
    int** resultMatrix = allocateMatrix(rows, cols);

    // Step 3: Read elements for Matrix A
    printf("\n--- For Matrix A ---\n");
    readMatrix(matrixA, rows, cols);

    // Step 4: Read elements for Matrix B
    printf("\n--- For Matrix B ---\n");
    readMatrix(matrixB, rows, cols);

    // Step 5: Add the two matrices
    addMatrices(matrixA, matrixB, resultMatrix, rows, cols);

    // Step 6: Print the matrices and their sum
    printf("\n--- Matrix A ---\n");
    printMatrix(matrixA, rows, cols);

    printf("\n--- Matrix B ---\n");
    printMatrix(matrixB, rows, cols);

    printf("\n--- Sum Matrix (A + B) ---\n");
    printMatrix(resultMatrix, rows, cols);

    // Step 7: Free dynamically allocated memory
    freeMatrix(matrixA, rows);
    freeMatrix(matrixB, rows);
    freeMatrix(resultMatrix, rows);

    return 0;
}