primefactorization.go

// prime factorization for n
func getPrimeFactorization(n int) ([]int) {
	var primefactors []int
	
	// check divisibility by 2,3 and all odd numbers up to n
	var divider = append([]int{2}, getOddNumbers(n)...)
	for _, i := range divider {
		for n % i == 0 {
			primefactors = append(primefactors, i)
			n = n / i
		}
		if i > n {
			break
		}
	}
	return primefactors
}

// prime factorization numbers for n (no number double) - e.g: regular: 4 = [2 2] - here: 4 = [2]
func getPrimeFactorizationNumbers(n int) ([]int) {
	var primefactors []int
	
	// check divisibility by 2,3 and all odd numbers up to n
	var divider = append([]int{2}, getOddNumbers(n)...)
	for _, i := range divider {
		for n % i == 0 {
			if !sliceContains(primefactors, i) {
				primefactors = append(primefactors, i)
			}
			n = n / i
		}
		if i > n {
			break
		}
	}
	return primefactors
}

// returns slice of every odd number to n, including 2
func getOddNumbers(n int) ([]int){
	var numbers []int
	for i := 3; i <= n; i = i +2 {
		numbers = append(numbers, i)
	}
	return numbers
}

func sliceContains(s []int, e int) bool {
    for _, a := range s {
        if a == e {
            return true
        }
    }
    return false
}