LeetCode

Problem Statement

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

Solution

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
	dummy := ListNode{}
	head := &dummy
	carry := 0

	for l1 != nil || l2 != nil || carry != 0 {
		sum := 0

		if l1 != nil {
			sum += l1.Val
			l1 = l1.Next
		}
		if l2 != nil {
			sum += l2.Val
			l2 = l2.Next
		}

		sum += carry
		carry = sum / 10

		head.Next = &ListNode{Val: sum % 10}
		head = head.Next
	}

	return dummy.Next
}