002.md

2. Add Two Numbers

Solution 1

/**
 * 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 *dummy = new ListNode(-1);
        ListNode *p = dummy;
        int carry = 0;
        while (l1 != NULL || l2 != NULL || carry != 0) {
            if (l1 != NULL) {
                carry += l1->val;
                l1 = l1->next;
            }
            if (l2 != NULL) {
                carry += l2->val;
                l2 = l2->next;
            }
            if (carry >= 10) {
                p->next = new ListNode(carry - 10);
                carry = 1;
            } else {
                p->next = new ListNode(carry);
                carry = 0;
            }
            p = p->next;
        }
        return dummy->next;
    }
};