19.1.29 [LeetCode 21] Merge Two Sorted Lists

Posted 2021-02-06

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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

 1 class Solution {
 2 public:
 3     ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
 4         ListNode*head=new ListNode(0);
 5         ListNode*ans = head;
 6         while (l1&&l2) {
 7             if (l1->val < l2->val) {
 8                 head->next = l1;
 9                 l1 = l1->next;
10             }
11             else {
12                 head->next = l2;
13                 l2 = l2->next;
14             }
15             head = head->next;
16         }
17         if (l1)head->next = l1;
18         else if (l2)head->next = l2;
19         return ans->next;
20     }
21 };

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