;eetcode刷题 21. Merge Two Sorted Lists

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21. Merge Two Sorted Lists

题目描述

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.
Example:
Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

代码

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
    ListNode head(0);       //这里还是不是很清楚为什么声明为指针的会出错。
    ListNode* cur;
    cur = &head;
    while(l1 != nullptr || l2 != nullptr)
    {
        if(!l1) 
        {
            cur->next = l2;
            break;
        }
        if(!l2)
        {
            cur->next = l1; 
            break;
        }
            
        if(l1->val <= l2->val)  
        {  
            cur->next = l1;
            l1 = l1->next;
        }
        else 
        {
            cur->next = l2;
            l2 = l2->next;
        }
        cur=cur->next;
    }
    return head.next;
}
};