# 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):
if l1 == None and l2:
return l2
if l2 == None and l1:
return l1
p_head=p=ListNode(0)
while l1 and l2:
if l1.val<=l2.val:
p.next=l1 #p最開始在頭結點處,所以爲p.next
l1=l1.next
else:
p.next=l2
l2=l2.next
p=p.next
if l1:
p.next=l1
if l2:
p.next=l2
return p_head.next
"""
:type l1: ListNode
:type l2: ListNode
:rtype: ListNode
"""