Question

Add a function int countPrimes(int a, int b); that returns the number of prime numbers in the interval a ≤ x ≤ b. Change the main function to test the new code.

Please, it needs to be a function above/before the main function and it is necessary to use the given names. Thanks

Answer 1

#include <iostream>
using namespace std;
int countPrimes(int a, int b);
int main(){
int a,b;
cout<<"Enter lower limit: ";
cin>>a;
cout<<"Enter upper limit: ";
cin>>b;
cout<<countPrimes(a,b);
return 0;

}
int countPrimes(int a, int b)
{
int flag,count=0;
while (a<=b) //starts from lower limit to upper limit
{
flag = 0;
for(int i=2;i<=a/2; ++i)
{
if(a%i==0)
{
flag=1;
break;
}
}
if(flag==0&&a>1) //checks if a is greater than 1
count++;
a++;
}
return count;
}