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C++ Exercises: Check whether a number is prime or not

C++ For Loop: Exercise-5 with Solution

Write a program in C++ to check whether a number is prime or not.

Pictorial Presentation:

C++ Exercises: Check whether a number is prime or not

Sample Solution :-

C++ Code :

#include <iostream>
using namespace std;
int main()
{
    int num1, ctr = 0;
    cout << "\n\n Check whether a number is prime or not:\n";
	cout << "--------------------------------------------\n";
	cout << " Input a number to check prime or not: ";
	cin>> num1;	
    for (int a = 1; a <= num1; a++) 
    {
        if (num1 % a == 0) 
        {
            ctr++;
        }
    }
    if (ctr == 2) 
    {
        cout << " The entered number is a prime number. \n";
    }
    else {
        cout << " The number you entered is not a prime number. \n";
    }
}

Sample Output:

 Check whether a number is prime or not:                               
--------------------------------------------                           
 Input a number to check prime or not: 13                              
 The entered number is a prime number. 

Flowchart:

Flowchart: Check whether a number is prime or not

C++ Code Editor:

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C++ Programming: Tips of the Day

What is a smart pointer and when should I use one?

This answer is rather old, and so describes what was 'good' at the time, which was smart pointers provided by the Boost library. Since C++11, the standard library has provided sufficient smart pointers types, and so you should favour the use of std::unique_ptr, std::shared_ptr and std::weak_ptr.

There was also std::auto_ptr. It was very much like a scoped pointer, except that it also had the "special" dangerous ability to be copied - which also unexpectedly transfers ownership.

It was deprecated in C++11 and removed in C++17, so you shouldn't use it.

std::auto_ptr<MyObject> p1 (new MyObject());
std::auto_ptr<MyObject> p2 = p1; // Copy and transfer ownership. 
                                 // p1 gets set to empty!
p2->DoSomething(); // Works.
p1->DoSomething(); // Oh oh. Hopefully raises some NULL pointer exception.

Ref : https://bit.ly/3mc9GHE