[Leetcode]2. 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

这个题目比较简单，一个节点一个节点加即可，要注意进位。

/** * 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 carry = 0;        ListNode *t = new ListNode(0);        ListNode *ptr = t, *p = l1, *q = l2;        while(p != NULL || q != NULL)        {            int val1 = 0;            if(p != NULL)            {                val1 = p->val;                p = p->next;            }            int val2 = 0;            if(q != NULL)            {                val2 = q->val;                q = q->next;            }            int temp = val1 + val2 + carry;            ptr->next = new ListNode(temp % 10);            carry = temp / 10;            ptr = ptr->next;        }        if(carry == 1)            ptr->next = new ListNode(1);        return t->next;    }};