module euler
import math

pub fn range(start int, end int) []int {
	mut result := []int
	for i := start; i <= end; i++ {
		result << i
	}
	return result
}

pub fn even(n int) bool {
	return n % 2 == 0
}

pub fn prime(n u64) bool {
	for i := u64(2); i <= u64(math.sqrt(f64(n))); i++ {
		if n % i == 0 {
			return false
		}
	}
	return true
}

pub fn factors(n u64) []u64 {
	mut factors := []u64
	for i := u64(2); i <= u64(math.sqrt(f64(n))); i++ {
		if n % i == 0 && prime(i) {
			factors << i
		}
	}
	return factors
}

pub fn max(ints []u64) u64 {
	mut max := u64(0)
	for n in ints {
		if n > max {
			max = n
		}
	}
	return max
}

pub fn two_combinations(ints []int) [][]int {
	mut result := [[]int]
	result = []
	for i := 0; i < ints.len; i++ {
		for j := i + 1; j < ints.len; j++ {
			result << [[ints[i], ints[j]]]
		}
	}
	return result
}

pub fn palindrome(n int) bool {
	str := n.str()
	for i := 0; i < str.len; i++ {
		if str[i] != str[str.len-1-i] {
			return false
		}
	}
	return true
}