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C++ Exercises: Find prime number within a range

C++ For Loop: Exercise-6 with Solution

Write a program in C++ to find prime number within a range.

Sample Solution:

C++ Code:

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
	int num1,num2;
    int fnd=0,ctr=0;
    cout << "\n\n Find prime number within a range:\n";
	cout << "--------------------------------------\n";
	cout << " Input number for starting range: ";
	cin>> num1;
	cout << " Input number for ending range: ";
	cin>> num2;		

	cout << "\n The prime numbers between "<<num1<<" and "<<num2<<" are:"<<endl;
    for(int i=num1;i<=num2;i++)
       {
           for(int j=2;j<=sqrt(i);j++)
               {
               if(i%j==0)
                  ctr++;
               }
               if(ctr==0&&i!=1)
               { fnd++;
                 cout<<i<<" ";
                 
               }
               ctr=0;
       }
 cout<<"\n\n The total number of prime numbers between "<<num1<<" to "<<num2<<" is: "<<fnd<<endl;
 return 1;
}

Sample Output:

 Find prime number within a range:                                     
--------------------------------------                                 
 Input number for starting range: 1                                    
 Input number for ending range: 100                                    
                                                                       
 The prime numbers between 1 and 100 are:                              
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 
                                                                       
 The total number of prime numbers between 1 to 100 is: 25  

Flowchart:

Flowchart: Find prime number within a range

C++ Code Editor:

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Previous: Write a program in C++ to check whether a number is prime or not.
Next: Write a program in C++ to find the factorial of a number.

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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