leetcode 21. 合并两个有序链表

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

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

class Solution:
    def mergeTwoLists(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        res = []
        while l1:
            res.append(l1.val)
            l1 = l1.next
            
        while l2:
            res.append(l2.val)
            l2 = l2.next
            
        res.sort()
        
        l = ListNode(0)
        p = l
        for i in res:
            node = ListNode(i)
            p.next = node
            p = p.next
        return l.next