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

这题意思是，数字是反过来存储在linkedlist里的，比如上面那个其实就是计算
342+465 = 807的过程。
这题最好的解法是programcreek里提供的，利用while()里面的||循环，非常简洁易懂。相比之下code ganker还有其他一些人的解法就繁琐多了，他们的while循环是用&&的，导致需要分别处理l1和l2!=null的情况，非常复杂。以后还是多看几种解法比较好。

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

        int carry = 0;

        ListNode p1 = l1, p2 = l2, fakeHead = new ListNode(-1), p3 = fakeHead;

        while (p1 != null || p2 != null) {
            if (p1 != null) {
                carry += p1.val;
                p1 = p1.next;
            }
            if (p2 != null) {
                carry += p2.val;
                p2 = p2.next;
            }

            p3.next = new ListNode(carry % 10);
            p3 = p3.next;
            carry = carry / 10;
        }
        //别忘了
        if (carry == 1)
            p3.next = new ListNode(carry);
        
        
        return fakeHead.next;
    }

另外，code ganker提到了这题是CC150里的。可以看看。

reference:
http://www.cnblogs.com/springfor/p/3864493.html