C++ Program to Print a 2D Array

A 2D array in C++ stores elements in rows and columns and can be traversed using nested loops.
The elements can be printed row by row using traditional for loops or range-based for loops.

• The outer loop traverses the rows, while the inner loop traverses the columns.
• Both approaches take O(n × m) time for an array with n rows and m columns.

Examples:

Input: {{1, 2, 3},
           {4, 5, 6},
           {7, 8, 9}}
Output: 1 2 3 
              4 5 6
              7 8 9

Input: {{11, 12, 13},
            {14, 15, 16}}
Output: 11 12 13
              14 15 16

Approaches to Print a 2D Array

A 2D array can be printed using the following approaches:

Printing a 2D Array Using Nested for Loops

The traditional approach uses two nested for loops. The outer loop traverses the rows, and the inner loop traverses the elements of each row.

Steps:

1. Start from the first row.
2. Traverse each element in the current row.
3. Print every element followed by a space.
4. Move to the next line after completing a row.
5. Repeat until all rows are printed.

#include <iostream>
using namespace std;

int main()
{
    const int rows = 3;
    const int cols = 3;

    int arr[rows][cols] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };

    for (int i = 0; i < rows; i++)
    {
        for (int j = 0; j < cols; j++)
        {
            cout << arr[i][j] << " ";
        }

        cout << '\n';
    }

    return 0;
} 

1 2 3 
4 5 6 
7 8 9 

Explanation: The outer loop selects each row, while the inner loop accesses every element in that row. After printing all elements of a row, '\n' moves the output to the next line.

Printing a 2D Array Using a Range-Based for Loop

C++ also provides range-based for loops, which allow direct traversal of the elements without explicitly managing array indices.

Steps:

1. Traverse each row using the outer range-based for loop.
2. Traverse each element of the current row using the inner loop.
3. Print each element.
4. Move to the next line after completing each row.

#include <iostream>
using namespace std;

int main()
{
    int matrix[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };

    for (const auto& row : matrix)
    {
        for (const auto& element : row)
        {
            cout << element << " ";
        }

        cout << '\n';
    }

    return 0;
} 

1 2 3 
4 5 6 
7 8 9 

Explanation: The outer loop iterates over each row of the 2D array, while the inner loop iterates over the elements in that row. Using const auto& avoids unnecessary copying while keeping the elements read-only during traversal.