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

rina j. kadam

rina j. kadam

@rina-j-kadam-nUN9Iv • Oct 16, 2024
what is the condition for prime numbers in c++ as well as javascript?
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  • Saandeep Sreerambatla

    Saandeep Sreerambatla

    @saandeep-sreerambatla-hWHU1M • Feb 26, 2013

    Do you mean the logic?
    As far as I know the logic will be same in any programming language you do it.
    0
  • simplycoder

    simplycoder

    @simplycoder-NsBEdD • Feb 26, 2013

    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<number_you_want_to_test;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.
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