2 Add Two Numbers

You are given twonon-emptylinked lists representing two non-negative integers. The digits are stored inreverse orderand 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.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode result = new ListNode(-1);
        ListNode current = result;
        int carry = 0;

        while (l1 != null || l2 != null) {
            int num1 = 0, num2 = 0;
            if (l1 != null) {
                num1 = l1.val;
                l1 = l1.next;
            }
            if (l2 != null) {
                num2 = l2.val;
                l2 = l2.next;
            }
            current.next = new ListNode((num1+num2+carry)%10);
            current = current.next;
            carry = (num1+num2+carry)/10;
        }
        if (carry > 0) {
            current.next = new ListNode(carry);
        }
        return result.next;
    }
}