题意

2. 两数相加

题解

方法一：模拟

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        int carry = 0;
        ListNode* head = new ListNode(-1);
        ListNode* pre = head;
        while (l1 || l2 || carry) {
            int num = (l1 != nullptr ? l1->val : 0) + (l2 != nullptr ? l2->val : 0) + carry;
            carry = num / 10;
            ListNode* node = new ListNode(num % 10);
            pre->next = node;
            pre = node;
            l1 = l1 ? l1->next : nullptr;
            l2 = l2 ? l2->next : nullptr;
        }
        return head->next;
    }
};