Is A Number Prime?

Define a function that takes one integer argument and returns logical value true or false depending on if the integer is a prime.

Per Wikipedia, a prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself.

Requirements

• You can assume you will be given an integer input.
• You can not assume that the integer will be only positive. You may be given negative numbers as well (or 0).
• NOTE on performance: There are no fancy optimizations required, but still the most trivial solutions might time out. Numbers go up to 2^31 (or similar, depends on language version). Looping all the way up to n, or n/2, will be too slow.

Example

is_a_number_prime(1)  /* false */
is_a_number_prime(2)  /* true  */
is_a_number_prime(-1) /* false */

Solution

PYTHON

def is_a_number_prime(num):
    if num <= 1 or (num % 2 == 0 and num > 2):
        return False
    elif num == 2:
        return True
    else:
        for i in range(3, int(num**0.5) + 1, 2):
            if num % i == 0:
                return False
        return True


print(is_a_number_prime(4))