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。
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 = ListNode(0) #创建一个新的头节点
current_node = head #新链表的当前节点
while l1 != None and l2 != None: #l1和l2 存在
if l1.val > l2.val: #l1值大于l2,将l2值插进来,遍历l2
head.next = l2
l2 = l2.next
else :
head.next = l1
l1 = l1.next
head = head.next #一次比较后,继续遍历
if l1 == None:
head.next = l2
elif l2 == None:
head.next = l1
return current_node.next