What is the condition for prime numbers in c++ as well as javascript?

Replies

• 

  Saandeep Sreerambatla

  Do you mean the logic?
  As far as I know the logic will be same in any programming language you do it.
• 

  simplycoder

  Condition for prime would remain the same in js,c,C++... and any other language.
  Its typically same as paper-pencil logic -- If A number is divisible only by 1 and itself and has no other factors, then the number is said to be prime.
  
  
  Simplest logic would be using a for loop.
  
  something like this.
  
  boolean isPrime=true;
  for(int i=2;i
  {
  isPrime is true;
  if(number_you_want_to_test is divisible by i)
  {
  isPrime is false;
  the number is not prime, and break from the for loop.
  
  }
  
  }
  if(isPrime is true)
  the number is prime.
  
  Now you have many options to reduce the number of checks eg. instead of checking till number_you_want_to_test, you can check it number_you_want_to_test/2 think over this and why this is correct.
  
  After some more brain storming, you can see that this can be further reduced to checking only until square root of number_you_want_to_test with some changes.
  
  Brain storm more, you know that all even numbers are divisible by 2 so no even number which is greater than 2 would ever be a prime number, so think how can you avoid even numbers greater than 2. Once you do these things, you can implement advance algorithm like Sieves and such.