Prime numbers

Question

How do I find prime numbers less than a known number?

Answer 1

Roman J I haven't considered time complexity. If that's so, then for loop to sqrt(n) will be even more efficient

This will give time complexity of O(sqrt(n))

Answer 2

Look here, this should work perfectly:

https://www.sololearn.com/learn/969/?ref=app

Answer 3

#include <iostream>
using namespace std;
int main()
{
int n, i;
bool isPrime = true;
cout << "Enter a positive integer: ";
cin >> n;
for(i = 2; i <= n / 2; ++i)
{
if(n % i == 0)
{
isPrime = false;
break;
}
}
if (isPrime)
cout << "This is a prime number";
else
cout << "This is not a prime number";
return 0;
}

Answer 4

Make a Prime() function which contains a for loop i in the range between 2 and a num (say n). It will return False if n%i = = 0.
and then
return True. // will execute only if the above for loop doesn't return anything //

In the main function use another for loop in the range 2 to the input num (say p) . so primes are present between 2 and p.

int main()
{
for (i= 2 ; i<p;i++)
{
if( Prime(i) ==True)
cout<<i<<endl;
}

return 0;
}

Answer 5

1 is noy a prime number , but in ur code the opposit