[leetcode]Merge Two Sorted Lists @ Python

原题地址：https://oj.leetcode.com/problems/merge-two-sorted-lists/

题意：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.

解题思路：合并两个已经排好序的链表。

代码：

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

class Solution:
# @param two ListNodes
# @return a ListNode
def mergeTwoLists(self, l1, l2):
if l1 == None:
return l2
if l2 == None:
return l1
dummy = ListNode(0)
tmp = dummy
while l1 and l2:
if l1.val <= l2.val:
tmp.next = l1
l1 = l1.next
tmp = tmp.next
else:
tmp.next = l2
l2 = l2.next
tmp = tmp.next
if l2 == None:
tmp.next = l1
else:
tmp.next = l2
return dummy.next