Ruby determines whether a number is prime (prime) sample _ruby topics

Ruby determines whether a number is prime

Prime numbers are also called primes. A natural number greater than 1, if it is not divisible by other natural numbers except for 1 and itself, (except for 0), otherwise known as composite numbers. According to the basic theorem of arithmetic, each integer that is larger than 1 is either itself a prime number or a product of a series of prime numbers, and if the order of these primes in the product is not taken into account, the written form is unique.

Copy Code code as follows:

Def Prime? (num)
res = [1]
Res << num

If num = 0 | | num = 1
return False
End

2.upto (Ten) do |x|
#如果有自己的话, just skip the next round.
if num = = X
Next
End

Divide the number between #看看是否能被 2-10, and the remainder equals grouping
If num% x = 0
Res << x
End
End

Res.length > 2? False:true
End