> For the complete documentation index, see [llms.txt](https://garychang.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://garychang.gitbook.io/leetcode/21.-merge-two-sorted-lists.md).

# 21. Merge Two Sorted Lists

<https://leetcode.com/problems/merge-two-sorted-lists/description/>

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
```

**Solution:**&#x20;

```
# # Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def mergeTwoLists(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        if not l1 or not l2:
            return l1 or l2
        if l1.val < l2.val:
            l1.next = self.mergeTwoLists(l1.next, l2)
            return l1
        else:
            l2.next = self.mergeTwoLists(l1, l2.next)
            return l2
```