Optimizing prime numbers code?

Question

I wrote this code to show the primes between 1 and 100. The only condition is to do not use functions, whole code should be inline. I would ask if I can improve (optimize) it mu

Answer 1

You could optimise your existing code:

• In the while loop you should have a step of 2, so that you do not test the even numbers.
• In your for loop you should stop when you reach the square root of the number you are testing

You could use a different method:

• Sieve of Erastoses: http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes

On the Sieve of Erastoses just removing the numbers divisable by 2,3 and 5 would significantly reduce the number of times you need to test for primality.