Get random n rows from a 2D array in C++

This tutorial will show you how to get the random n number of rows from a 2D array in C++. The 2D array is nothing but a matrix which have rows and columns. We will generate n random numbers within the range of maximum and minimum number of rows to get any random number of rows.

Algorithm

Note: Refer to How to generate a random number in C++ module to get familiar with the rand() function.

Step 1: Define the 2D array of any data type. Define the value of n i.e. the number of random rows you want to get. But n should be less than or equal to the actual number of rows present in the 2D array.

Step 2: Then call the srand(unsigned int seed)to generate different random numbers at every execution.

Step 3: Run the loop n times. Then generate the random integer within the range of minimum and maximum number of rows. The formula to generate the random numbers within the range is (rand() % (max - min + 1)) + min
Here the minimum range would be 0 because the array indexes start from 0 and the maximum would be the index of a maximum number of rows present in a 2D array.

Step 4: Then print that particular row element using a loop for column elements.

C++ code for getting random n rows from a 2D array in C++

code:

#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
    int arr[4][4] = {{1, 0, 3, 2},
                     {4, 5, 2, 3},
                     {5, 8, 9, 0},
                     {2, 6, 7, 4}};
                     
    int n = 3;
    srand(time(0));
    
    for (int i = 0; i < n; i++)
    {
       int row = (rand() % 4); // (rand() % (3-0+1)) + 0
       std::cout << "row : " <<row << std::endl;
       
       for (int j = 0; j < 4; j++) 
       {
           cout << arr[row][j] << " ";
       }
       cout << endl;
    }
    
    return 0;
}

Output :

row : 1
4 5 2 3 
row : 3
2 6 7 4 
row : 0
1 0 3 2