solution for more optimized link_list

linked_list_add_optimized.go

func optimizedAddTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
	carry := 0
	sum := 0

  //this is the starting node, we need to return this
	head := ListNode{
		Val:  0,
		Next: nil,
	}
  //create a current node to save to
	var currentNode *ListNode
	currentNode = &head

forLoop:
	for l1 != nil || l2 != nil { //as long as both lists are not empty keep looping
		intermediate := 0
		switch {
		case l1 != nil && l2 != nil:
			intermediate = (l1.Val + l2.Val + carry)
			sum = intermediate % 10
			carry = intermediate / 10
			l1 = l1.Next
			l2 = l2.Next

		case l1 != nil:
			intermediate = (l1.Val + carry)
			sum = intermediate % 10
			carry = intermediate / 10
			l1 = l1.Next
		case l2 != nil:
			intermediate = (l2.Val + carry)
			sum = intermediate % 10
			carry = intermediate / 10
			l2 = l2.Next
		default:
			intermediate = carry
			sum = intermediate % 10
			carry = intermediate / 10
		}

		currentNode.Val = sum //save the sum to the currentNode
		nextNode := ListNode{ //initiate a nextNode
			Val:  0,
			Next: nil,
		}
		//breaking logic
		switch {
		case l1 == nil && l2 == nil && carry == 0: //if both numbers are nil, break out
			break forLoop
		case l1 == nil && l2 == nil && carry != 0: //if there is a carry but both nodes are nil, it needs to be added to the nextNode
			currentNode.Next = &nextNode
			currentNode = &nextNode
			currentNode.Val = carry
			break forLoop
		}
 
		currentNode.Next = &nextNode //if there are still nodes to explore set currentNode to equal nextNode
		currentNode = &nextNode
	}

	return &head

}