leetcode 2. Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers. 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.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

考察链表操作

/**
 * 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) {
        ListNode* h = new ListNode(0);
        ListNode* p = h; int r = 0;
        while(l1!=NULL || l2!=NULL){
            int v = (l1==NULL?0:l1->val)+(l2==NULL?0:l2->val)+r;
            p->next = new ListNode(v%10);p=p->next;
            r = v/10;
            if(l1)l1=l1->next;
            if(l2)l2=l2->next;
        }
        if(r)p->next=new ListNode(r);
        return h->next;
    }
};