Testing whether a number is a prime number with for loop. - C++ Statement

C++ examples for Statement:for

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Description

Testing whether a number is a prime number with for loop.

Demo Code

#include <iostream>
#include <cmath>
using namespace std;
int main()/*from w  w  w  .  j a  v  a  2s .c om*/
{
   int  n = 0;   // Number to test for prime-ness
   bool is_prime = true; // Boolean flag; assume true
   //   until proven otherwise
   // Get a number from the keyboard.
   cout << "Enter a number and press ENTER: ";
   cin >> n;
   // Test for prime by checking for divisibility by all whole numbers from 2 to sqrt(n).
   for (int i = 2; i <= sqrt(n); ++i) {
      if (n % i == 0) {
         is_prime = false;
      }
   }
   // Print results
   if (is_prime) {
      cout << "Number is prime." << endl;
   } else {
      cout << "Number is not prime." << endl;
   }
   return 0;
}

Result


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