[LeetCode]Add Two Numbers

题目描述：

You are given two linked lists representing two non-negative numbers. 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.

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

分类： 简单题

1A：False

坑点：当两个链表都走到了尽头，千万不要认为程序就此终止啊。如果借位不为零，还得为下一个节点赋值。我就是因为这个问题被一个这样的输入打回的：(A1失败...

Input  [5], [5]
Output [0]
Expect [0, 1]

程序：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode result = null;
        ListNode head = result;
        int v1 = 0, v2 = 0, v3 = 0, overflow = 0;
        while(l1 != null || l2 != null || overflow != 0) {
            v1 = v2 = 0;
            if (l1 != null) v1 = l1.val;
            if (l2 != null) v2 = l2.val;
            v3 = v1 + v2 + overflow;
            overflow = 0; //reset overflow
            if (v3 >= 10) {
                v3 -= 10;
                overflow = 1;
            }
            if (head == null) {
                head = new ListNode(v3);
                result = head;
            } else {
                head.next = new ListNode(v3);
                head = head.next;
            }
            if (l1 != null) l1 = l1.next;
            if (l2 != null) l2 = l2.next;
        }
        return result;
    }
}