leetcode刷题（java）——nums【2】

problem：

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：

/*
 * @lc app=leetcode id=2 lang=java
 *
 * [2] Add Two Numbers
 */
/**
 * 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 head = l1 != null ?l1:l2;
    ListNode tail = head;
        
        int sum = 0;
        int carry = 0;
        while (l1 != null || l2 != null) {
            sum = carry + (l1 != null ? l1.val : 0) + (l2 != null ? l2.val : 0);
            tail.val = sum % 10;
            carry = sum / 10;
            
            l1 = l1 != null ? l1.next : l1;
            l2 = l2 != null ? l2.next : l2;
            
            tail.next = l1 != null ? l1 : l2 != null ? l2 : carry != 0 ? new ListNode(carry) : null;
            tail = tail.next;
        }
        
        return head;
    }
}