2. Add Two Numbers

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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8

Code：

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } * @author liyiheng */ public class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { if (l1 == null && l2 == null) return null; ListNode temp = l1 == null ? l2 : l1; ListNode mayBeNull = l1 != null ? l2 : l1; int value1 = l1 == null ? 0 : l1.val; int value2 = l2 == null ? 0 : l2.val; int extra = (value1 + value2) / 10; temp.val = (value1 + value2) % 10; if (extra > 0) { if (temp.next != null) { temp.next.val += extra; } else { temp.next = new ListNode(extra); } } temp.next = addTwoNumbers(temp.next, mayBeNull == null ? null : mayBeNull.next); return temp; } }