【题解】21. 合并两个有序链表 (链表)

https://leetcode.cn/problems/merge-two-sorted-lists/description/

/**
 * 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* mergeTwoLists(ListNode* list1, ListNode* list2) {
        ListNode* newHead = new ListNode(0); // 初始化一个新的头节点
        ListNode* cur = newHead;
        while (list1 != nullptr && list2 != nullptr) {
            if (list1->val < list2->val) {
                cur->next = list1;
                cur = list1;
                list1 = list1->next;
            } else {
                cur->next = list2;
                cur = list2;
                list2 = list2->next;
            }
        }

        if (list1 != nullptr) {
            cur->next = list1;
        } else if (list2 != nullptr) {
            cur->next = list2;
        }

        return newHead->next; //返回新链表的头节点
    }
};