Example: Upper Triangular Matrix (User Input) in C++

// Upper Triangular Matrix (User Input)
#include <iostream>
#include <vector> // Required for dynamic arrays (vectors)

using namespace std;

int main() {
    int rows, cols;

    // Step 1: Get matrix dimensions from the user
    cout << "Enter the number of rows: ";
    cin >> rows;
    cout << "Enter the number of columns: ";
    cin >> cols;

    // Step 2: Declare a 2D vector (dynamic array) to store the matrix
    // This allows for matrices of arbitrary size determined at runtime
    vector<vector<int>> matrix(rows, vector<int>(cols));

    // Step 3: Get matrix elements from the user
    cout << "Enter the elements of the matrix (" << rows << "x" << cols << "):\n";
    for (int i = 0; i < rows; ++i) {
        for (int j = 0; j < cols; ++j) {
            cout << "Enter element at [" << i << "][" << j << "]: ";
            cin >> matrix[i][j];
        }
    }

    cout << "\nOriginal Matrix:\n";
    for (int i = 0; i < rows; ++i) {
        for (int j = 0; j < cols; ++j) {
            cout << matrix[i][j] << "\t"; // Using tab for better alignment
        }
        cout << endl;
    }

    cout << "\nUpper Triangular Matrix:\n";
    // Step 4: Iterate and display the upper triangular form
    for (int i = 0; i < rows; ++i) {
        for (int j = 0; j < cols; ++j) {
            if (j < i) {
                cout << "0\t"; // Print 0 for elements below the main diagonal
            } else {
                cout << matrix[i][j] << "\t"; // Print original element
            }
        }
        cout << endl;
    }

    return 0;
}