合并两个有序链表

将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。 

 

 

#include <iostream>

using namespace std;

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 *l1, ListNode *l2) {
        ListNode *prevNode = new ListNode(0);
        ListNode *cur = prevNode;
        while (l1 != nullptr && l2 != nullptr) {
            if (l1->val < l2->val) {
                cur->next = new ListNode(l1->val);
                cur = cur->next;
                l1 = l1->next;
            } else {
                cur->next = new ListNode(l2->val);
                cur = cur->next;
                l2 = l2->next;
            }
        }
        if (l1 != nullptr)
            cur->next = l1;
        if (l2 != nullptr)
            cur->next = l2;
        return prevNode->next;
    }
};