Golang method to determine whether it is a prime number

How to determine prime numbers: Use a number to divide 2 to sqrt (this number)-1 respectively. If it can be divided evenly, it means that the number is not a prime number, otherwise it is a prime number.

Determine whether it is a prime number:

func IsPrime(n int) bool {
	if n == 1 {
		return false
	}

	//从2遍历到n-1，看看是否有因子
	for i := 2; i < n; i++ {
		if n%i == 0 {
			//发现一个因子
			return false
		}
	}
	return true
}

Determine whether it is a prime number Optimization algorithm:

func IsPrimeII(n int) bool  {
	//偶数一定不是素数
	if n>2 && n % 2 == 0{
		return true
	}

	//从2遍历到n的方根，看看是否有因子
	for i := 2; i <= int(math.Ceil(math.Sqrt(float64(n)))); i++ {
		if n%i == 0 {
			//发现一个因子
			return false
		}
	}
	return true
}

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