w3resource

C++ Exercises: List non-prime numbers from 1 to an upperbound

C++ For Loop: Exercise-16 with Solution

Write a program in C++ to list non-prime numbers from 1 to an upperbound.

Pictorial Presentation:

C++ Exercises: List non-prime numbers from 1 to an upperbound

Sample Solution :-

C++ Code :

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

int main()
{
    int ult;
    cout << "\n\n List non-prime numbers from 1 to an upperbound:\n";
    cout << "----------------------------------------------------\n";
    cout << " Input the upperlimit: ";
    cin >> ult;
    cout << " The non-prime numbers are: " << endl;
    for (int num = 2; num <= ult; ++num) 
    {
        int mfactor = (int)sqrt(num);
        for (int fact = 2; fact <= mfactor; ++fact) 
        {
            if (num % fact == 0) 
            {
                cout << num << " ";
                break;
            }
        }
    }
    cout << endl;
    return 0;
}

Sample Output:

 List non-prime numbers from 1 to an upperbound:                       
----------------------------------------------------                   
 Input the upperlimit: 25                                              
 The non-prime numbers are:                                            
4 6 8 9 10 12 14 15 16 18 20 21 22 24 25

Flowchart:

Flowchart: List non-prime numbers from 1 to an upperbound

C++ Code Editor:

Contribute your code and comments through Disqus.

Previous: Write a program in C++ to asked user to input positive integers to process count, maximum, minimum, and average or terminate the process with -1.
Next: Write a program in C++ to print a square pattern with # character.

What is the difficulty level of this exercise?



Share this Tutorial / Exercise on : Facebook and Twitter

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