[Question]: Check if given number is prime ? Prime numbers are divisible by self & 1 only
Example prime number : 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59
#Approach 1: if the number is perfectly divisible by 2,3,5 Then it’s not prime.
func checkIfNumberIsPrime(_ n : Int) ->Bool {
if n <= 1 {return false}
if n == 2 || n == 3 || n == 5 {return true}
return !(n%2 == 0 || n%3 == 0 || n % 5 == 0)
}
let n = 7
let isPrime = checkIfNumberIsPrime(n)
print("The number is- ", isPrime) // true
Approach #2: Take a square root of the number & check from 2 onwards if it’s perfectly divisible it’s not prime.
func checkIfNumberIsPrime(_ n : Int) ->Bool {
if n <= 1 {return false}
for i in 2..<Int(sqrt(Double(n))) {
if i%2 == 0 { return false }
}
return true
}