[Leetcode] 002. Add Two Numbers

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

两个链表相加的问题，比较简单。
把这个当成位来处理就很简单了。
代码如下：

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    if(l1==null) return l2;
    if(l2==null) return l1;

    ListNode head = new ListNode(0);
    ListNode p = head;

    int tmp = 0;
    while(l1!=null || l2!=null || tmp!=0) {
        if(l1!=null) {
            tmp += l1.val;
            l1 = l1.next;
        }
        if(l2!=null) {
            tmp += l2.val;
            l2 = l2.next;
        }

        p.next = new ListNode(tmp%10);
        p = p.next;
        tmp = tmp/10;
    }
    return head.next;
}