[Leetcode] 2 - Add Two Numbers

原题链接： https://oj.leetcode.com/problems/add-two-numbers/

一道很正常的链表的简单题，看code应该很容易理解。这里就不附上讲解了。

/**
 * 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* head = NULL;
        ListNode** pp = &head;
        
        ListNode* p1 = l1;
        ListNode* p2 = l2;
        int carry = 0;
        while (p1 || p2 || carry) {
            int v1 = (p1 ? p1->val : 0);
            int v2 = (p2 ? p2->val : 0);
            int sum = v1 + v2 + carry;

            carry = sum / 10;
            *pp = new ListNode(sum % 10);
            pp = &(*pp)->next;
            if (p1) p1 = p1->next;
            if (p2) p2 = p2->next;
        }
        return head;
    }
};