Project 14: Prime Numbers. Write a program that reads in an integer that is grea

Question

Project 14: Prime Numbers. Write a program  that reads in an integer  that is greater than  2 (let's call it k)  and finds and prints all of the prime numbers between  3 and k.  A prime number is a number such that 1 and itself are the only numbers that evenly divide it (for example, 3, 5, 7, 11, 13, 17, ...).

One way to solve this problem is to use a doubly nested loop. The outer loop can iterate  from 3 to k  while the inner loop checks to see if the counter value  for the outer loop is prime. One way to see if number n  is prime is to loop from 2 to n-1  and if any of these numbers evenly divides n,  then n  cannot be prime. If none of the values  from 2 to n-1  evenly divides !n, then n  must be prime. (Note that there are several easy ways to make this algorithm more efficient.)

Input Details: The input consists of just one integer  which you may assume  is 3 or greater. There is no prompt.

Output  Details: Each prime number is printed at the beginning of a new line and is followed by the predicate "is a prime number."

Explanation / Answer

#include <iostream>
using namespace std;

int main()
{
bool isPrime=true;

int n ;

cout << enter the number ;

cin >> n ;


for(int primeCandidate=3; primeCandidate<=n; primeCandidate++)
{
//Reset isPrime to true
isPrime = true;

//Check the factors
for(int factor=2; factor<primeCandidate-1; factor++)
{
//If a factor is found, the number is not prime. No reason to check
//the rest of the numbers, so break out of this 'for' loop.
if(primeCandidate%factor == 0)
{
isPrime = false;
break;
}
}

//If the number is prime, print it.
if(isPrime == true)
{
cout<< primeCandidate << " is prime." << endl;
}
}

return 0;
}

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.