Function addTwoNumbers2

add_two_numbers_2/solution.go:59–103

(l1 *structures.ListNode, l2 *structures.ListNode)

}

func addTwoNumbers2(l1 *structures.ListNode, l2 *structures.ListNode) *structures.ListNode {
	carry := 0
	sumList := &structures.ListNode{
		Val:  0,
		Next: nil,
	}
	frontSumList := sumList

	for l1 != nil || l2 != nil {
		// calculate sum and carry values
		l1Val := 0
		l2Val := 0
		if l1 != nil {
			l1Val = l1.Val
			l1 = l1.Next
		}
		if l2 != nil {
			l2Val = l2.Val
			l2 = l2.Next
		}

		sum := l1Val + l2Val + carry
		carry = sum / 10
		sumList.Val = sum % 10

		// no more list to process, but carry is not 0
		if l1 == nil && l2 == nil && carry > 0 {
			sumList.Next = &structures.ListNode{
				Val:  carry,
				Next: nil,
			}
		}

		// one or both lists still can be processed
		if l1 != nil || l2 != nil {
			sumList.Next = &structures.ListNode{
				Val:  0,
				Next: nil,
			}
			sumList = sumList.Next
		}
	}

	return frontSumList
}