C++ Exercises: Check if a number is Mersenne number or not

Last update on December 20 2024 12:24:33 (UTC/GMT +8 hours)

Write a C++ program to check if a number is a Mersenne number or not.

Sample Solution:

C++ Code :

# include <iostream> // Including input-output stream library
# include <math.h> // Including math library for mathematical functions
using namespace std; // Using the standard namespace

int main() // Start of the main function
{
    int n, p, ans, i, n1; // Declaring variables for storing input, power, answer, and loop control
    double result; // Declaring a variable for storing the result of mathematical operations

    cout << "\n\n Check whether a given number is a Mersenne number or not:\n"; // Display purpose
    cout << "------------------------------------------------------------\n"; // Display purpose
    cout << " Input a number: "; // Prompting user for input
    cin >> n; // Taking user input

    n1 = n + 1; // Calculating n+1 for further comparison

    p = 0; // Initializing 'p' variable to store powers of 2
    ans = 0; // Initializing 'ans' variable to determine if the number is Mersenne or not

    for (i = 0;; i++) // Start of an infinite loop to generate powers of 2
    {
        p = (int)pow(2, i); // Calculating powers of 2 using the 'pow' function

        if (p > n1) // If the calculated power exceeds the modified number 'n1', exit the loop
        {
            break;
        }
        else if (p == n1) // If the calculated power equals the modified number 'n1', it's a Mersenne number
        {
            cout << " " << n << " is a Mersenne number." << endl; // Displaying the result
            ans = 1; // Setting the 'ans' variable to indicate the number is a Mersenne number
        }
    }

    if (ans == 0) // If 'ans' is still 0, it means the number is not a Mersenne number
    {
        cout << " " << n << " is not a Mersenne number." << endl; // Displaying the result
    }
}

Sample Output:

 Check whether a given number is Mersenne number or not:               
------------------------------------------------------------           
 Input a number: 31                                                    
 31 is a Mersenne number.

Flowchart:

C++ Code Editor:

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