Eric 的小站

1
输入：l1 = [1,2,4], l2 = [1,3,4]
2
输出：[1,1,2,3,4,4]

1
输入：l1 = [], l2 = []
2
输出：[]

1
/**
2
 * Definition for singly-linked list.
3
 * struct ListNode {
4
 *     int val;
5
 *     ListNode *next;
6
 *     ListNode() : val(0), next(nullptr) {}
7
 *     ListNode(int x) : val(x), next(nullptr) {}
8
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
9
 * };
10
 */
11
class Solution {
12
public:
13
    ListNode* mergeTwoLists(ListNode* list1, ListNode* list2) {
14
        if (list1 == NULL)
15
            return list2;
16
        if (list2 == NULL)
17
            return list1;
18
        ListNode* result = new ListNode();
19
        ListNode* head = result;
20
        while (list1 != nullptr && list2 != nullptr) {
21
            if (list1->val <= list2->val) {
22
                head->next = list1;
23
                list1 = list1->next;
24
            } else {
25
                head->next = list2;
26
                list2 = list2->next;
27
            }
28
            head = head->next;
29
        }
30
        head->next = (list1 != nullptr) ? list1 : list2;
31
        return result->next;
32
    }
33
};