[C++][Units]质数判断

这个算法比较全面了，复杂度比较低。没有使用SB的递归，转而使用递减的除数来判定。

bool isPrime(int number) 
{
    //ignore negative sign
    number = abs(number);
    // 0 and 1 are prime numbers
    if (number == 0 || number == 1) {
        return true;
    }
    //find divisor that divides without a remainder
    int divisor;
    for (divisor = number/2; number%divisor != 0; --divisor) {
        ;
    }
    //if no divisor greater than 1 is found, it is a prime number
    return divisor == 1;
}