2D Array

Program to work with 2D arrays (matrices)

IntermediateTopic: Array Programs
Back

C++ 2D Array Program

This program helps you to learn the fundamental structure and syntax of C++ programming.

Try This Code
#include <iostream>
using namespace std;

int main() {
    int rows, cols;
    
    cout << "Enter number of rows: ";
    cin >> rows;
    cout << "Enter number of columns: ";
    cin >> cols;
    
    int matrix[rows][cols];
    
    cout << "Enter matrix elements:" << endl;
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            cin >> matrix[i][j];
        }
    }
    
    cout << "Matrix:" << endl;
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            cout << matrix[i][j] << " ";
        }
        cout << endl;
    }
    
    return 0;
}
Output
Enter number of rows: 3
Enter number of columns: 3
Enter matrix elements:
1 2 3
4 5 6
7 8 9
Matrix:
1 2 3
4 5 6
7 8 9

Understanding 2D Array

A 2D array (matrix) is an array of arrays. We use nested loops to read and display elements. The first index represents the row, and the second index represents the column. This structure is useful for representing tabular data.

Note: To write and run C++ programs, you need to set up the local environment on your computer. Refer to the complete article Setting up C++ Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your C++ programs.

Practical Learning Notes for 2D Array

This C++ program is part of the "Array Programs" topic and is designed to help you build real problem-solving confidence, not just memorize syntax. Start by understanding the goal of the program in plain language, then trace the logic line by line with a custom input of your own. Once you can predict the output before running the code, your understanding becomes much stronger.

A reliable practice pattern is to run the original version first, then modify only one condition or variable at a time. Observe how that single change affects control flow and output. This deliberate style helps you understand loops, conditions, and data movement much faster than copying full solutions repeatedly.

For interview preparation, explain this solution in three layers: the high-level approach, the step-by-step execution, and the time-space tradeoff. If you can teach these three layers clearly, you are ready to solve close variations of this problem under time pressure.

Previous
Merge Arrays

Table of Contents