Example: Display Upper Triangular Matrix in C++

// Display Upper Triangular Matrix
#include <iostream> // Required for input/output operations
#include <vector>   // Required for std::vector (dynamic arrays)
#include <iomanip>  // Required for std::setw (output formatting)

int main() {
    // Step 1: Define the size of the square matrix
    int size = 3; // For a 3x3 matrix

    // Step 2: Initialize the matrix with some values
    // Using a 2D vector for dynamic sizing and ease of use
    std::vector<std::vector<int>> matrix = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };

    // You can also get user input for the matrix elements:
    /*
    std::cout << "Enter " << size * size << " elements for the " << size << "x" << size << " matrix:\n";
    for (int i = 0; i < size; ++i) {
        for (int j = 0; j < size; ++j) {
            std::cout << "Enter element at (" << i + 1 << "," << j + 1 << "): ";
            std::cin >> matrix[i][j];
        }
    }
    */

    // Step 3: Display the original matrix (optional, for comparison)
    std::cout << "Original Matrix:\n";
    for (int i = 0; i < size; ++i) {
        for (int j = 0; j < size; ++j) {
            std::cout << std::setw(3) << matrix[i][j]; // setw(3) for alignment
        }
        std::cout << std::endl;
    }
    std::cout << "\n";

    // Step 4: Display the Upper Triangular Matrix
    std::cout << "Upper Triangular Matrix:\n";
    for (int i = 0; i < size; ++i) { // Iterate through rows
        for (int j = 0; j < size; ++j) { // Iterate through columns
            // Condition for upper triangular part: column index >= row index (j >= i)
            if (j >= i) {
                std::cout << std::setw(3) << matrix[i][j]; // Print the actual element
            } else {
                std::cout << std::setw(3) << 0; // Print '0' for elements below the main diagonal
            }
        }
        std::cout << std::endl; // Move to the next line after each row
    }

    return 0;
}