How to check a number isPrime using C++?

Preferred using bool isPrime(int number)


{


}

How to check a number isPrime using C++?
The largest possible factor of a number is number / 2 (if you think about this you should be able to verify it in your mind.)





int maxFactor = number / 2;


int testNumber = 2; //don't start at 1, everything is divisible by 1





if(number %26lt; 0)


{


throw logic_error;


}





while(testNumber %26lt;= maxFactor)


{


if(number % testNumber == 0) //if it divides evenly


{


return false;


}


else if(testNumber!=2)


{


testNumber+=2;


}


else if(testNumber == 2)


{


testnumber++;


}


return true;


}
Reply:You can do it quicker by only checking odd numbers after 3, and by stopping the search at the tested number's square root (rounded down to an integer).
Reply:Just like what lansingstudent09101 said but I am not exactly a C++ programmer although i did do it from age 8-11 (trust me i new how to do a lot) but make the int variables any thing you want but change the increment to NULL

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