LeetCode 02 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
分析：

题目要求将链表表示的两个数相加，如题目中 342 + 465 = 807.

该题目不难，主要是链表的基本操作。

需要注意的是：

1、两个链表可能不一样长

2、相加时可能产生进位。

代码如下：

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
     ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
        int x, y, z=0;
        ListNode *h =NULL, *t = NULL;
        while (l1!=NULL && l2!=NULL) {
            x= l1->val;
            y= l2->val;
            
            z= z+x+y;
            ListNode *node = new ListNode(z%10);
            if (h == NULL) {
                h= t = node;
            }else{
                t->next = node;
                t = node;
            }
            l1 = l1->next;
            l2 = l2 ->next;
            z = z/10;
        }
        ListNode * tmp= (l1 == NULL) ? l2:l1;
        while (tmp != NULL) {
            x= tmp->val;
            z= z+x;
            ListNode *node = new ListNode(z%10);
            if (h == NULL) {
                h= t = node;
            }else{
                t->next = node;
                t = node;
            }
            tmp = tmp->next;
            z = z/10;
        }
        if (z > 0) {
            ListNode *node = new ListNode(z%10);
            t->next = node;
            z = z/10;
        }
        
        
        return h;
    }
};