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。
示例:
---
输入:1->2->4, 1->3->4
输出:1->1->2->3->4->4
# 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
"""
head = idx = ListNode(None)
while l1!=None or l2!=None:
if l2==None or (l1!=None and l1.val <= l2.val):
# if判断中一开始少了 `l1!=None` 是不行的,l1空l2不空的时候不能进行l1.val <= l2.val
idx.next = l1
idx = idx.next
l1 = l1.next
else:
idx.next = l2
idx = idx.next
l2 = l2.next
return head.next
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