linked_list_add.go

//struct we will use for Linked list
type ListNode struct {
	Val  int
	Next *ListNode
}

//the function that puts it all together
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
	n1 := createNumber(l1)
	n2 := createNumber(l2)

	sum := n1 + n2

	fmt.Printf("%d + %d = %d \n", n1, n2, sum)

	return createLinkedList(int64(sum))
}

//create number from reversed linked-list
func createNumber(l *ListNode) int {
	val := l.Val
	decimalCount := 1
	for l.Next != nil { //iterate until nil
		l = l.Next
		computation := (l.Val * power(10, decimalCount))
		val += computation
		decimalCount++
	}
	return val
}

//create linked-list from int
func createLinkedList(n int) *ListNode {
	head := ListNode{
		Val:  int(n % 10),
		Next: nil,
	}

	var currentNode *ListNode
	currentNode = &head

	for n > 0 {
		n = n / 10
		nextNode := ListNode{
			Val:  int(n % 10),
			Next: nil,
		}
		if n == 0 {
			break
		}
		currentNode.Next = &nextNode
		currentNode = &nextNode
	}
	return &head
}

//debug printing function if you need it!
func printLinkedList(l *ListNode) {
	i := 1
	for l != nil { //iterate until nil
		fmt.Printf("%v: %v \n", i, l.Val)
		i++
		l = l.Next
	}
}

//helper function for exponents
func power(base int, power int) int {
	val := 1
	for i := 0; i < power; i++ {
		val *= base
	}
	return val
}