Print the Corner Elements and their Sum in a 2-D Matrix in C++

The task is to display the sum of all the corner elements stored in an array given a 2X2 array. The corner components of a matrix with row "r" and column "c" starting from zero will be mat[0][0], mat[0][c-1], mat[r-1][0], and mat[r-1][c-1]. To print the result on the screen, you must now gather these corner elements, i.e., mat[0][0] + mat[0][c-1] + mat[r-1][0] + mat[r-1][c-1].

Example:

If the given Matrix is:-

          3        6       

          2        5       

The output sum of the matrix should be 16

Algorithm:

• Start
• Step 1 -> create macro for rows and column as #define row 3 and #define col 3
• Step 2 -> main()
• Declare int sum=0 and array as arr[row][col] and variables int i,j,n
• Loop For i=0 and i<3 and i++
• Loop For j=0 and j<3 and j++
• Input arr[i][j]
• End
• End
• Print [0][0] + arr[0][row-1] +arr[col-1][0] + arr[col-1][row-1]
• Stop

Program:

Let's take an example to print the Corner Elements and their Sum in a 2-D Matrix in C++:

#include 

using namespace std;

int main() {

    int rows, cols;

    cout << "Enter the number of rows: ";

    cin >> rows;

    cout << "Enter the number of columns: ";

    cin >> cols;

    if (rows <= 0 || cols <= 0) {

        cout << "Invalid input for rows or columns. Exiting the program." << endl;

        return 1;

    }

    int matrix[rows][cols];

    cout << "Enter the elements of the matrix:" << endl;

    for (int i = 0; i < rows; i++) {

        for (int j = 0; j < cols; j++) {

            cin >> matrix[i][j];

        }

    }

    if (rows < 2 || cols < 2) {

        cout << "The matrix must have at least 2 rows and 2 columns to have corner elements." << endl;

    } else {

        int sumOfCorners = matrix[0][0] + matrix[0][cols - 1] + matrix[rows - 1][0] + matrix[rows - 1][cols - 1];

        cout << "Corner elements of the matrix:" << endl;

        cout << "Top-left: " << matrix[0][0] << endl;

        cout << "Top-right: " << matrix[0][cols - 1] << endl;

        cout << "Bottom-left: " << matrix[rows - 1][0] << endl;

        cout << "Bottom-right: " << matrix[rows - 1][cols - 1] << endl;

        cout << "Sum of corner elements: " << sumOfCorners << endl;

    }

    return 0;

}

Output:

Explanation:

1. User Input: In this example, the program first asks the user how many rows and columns there are in a 2-D matrix.
2. Input Validation: It verifies that the input values for the rows and columns are legitimate positive integers. In such a case, it alerts the user and ends the program.
3. Matrix Declaration: According to the user's input for the number of rows and columns, the program declares a 2-D array (matrix) to hold the matrix elements.
4. Input for the matrix: The user is prompted to enter the matrix's components. These values are read by the program and entered into the matrix array.
5. Corner Element Check: The program verifies the matrix's corner elements to see if there are at least two rows and two columns. A matrix must have at least two rows and two columns to have the four separate corner components (top-left, top-right, bottom-left, bottom-right). Therefore, this check is mandatory.
6. Calculation of the Corner Element: If the matrix meets the requirement for having corners, the program sums the four corner elements. It combines the values of the elements in the top-left, top-right, bottom-left, and bottom-right positions.
7. Output: After that, the program prints the values of the corner elements and their sum.