LeetCode——002 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.

** Solution: **

The questions were very simple, straightforward sum on the line

class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode *result = new ListNode(0);//记住，这是带头节点的
        ListNode *p = result, *p1 = l1, *p2 = l2;
        int c = 0;//进位
        while (p1 || p2)
        {
            int sum = (p1 ? p1->val : 0) + (p2 ? p2->val : 0) + c;
            p->next = new ListNode(sum % 10);
            p = p->next;
            c = sum / 10;
            p1 = p1 ? p1->next : nullptr;
            p2 = p2 ? p2->next : nullptr;
        }       
        if (c > 0)
            p->next = new ListNode(c);
        return result->next;
    }
};