合并两个排序的链表 python

输入两个单调递增的链表，输出两个链表合成后的链表，当然我们需要合成后的链表满足单调不减规则。

第一种方法递归：

class Solution:
	def Merge(self, pHead1, pHead2):
		if pHead1 == None:
			return pHead2
		elif pHead2 ==None:
			return pHead1
		
		pMergeHead = None
		if pHead1.val < pHead2.val:
			pMergeHead = pHead2
			pMergeHead.next = self.Merge(pHead1.next, pHead2)
		else:
			pMergeHead = pHead1
			pMergeHead.next = self.Merge(pHead1, pHead2.next)
		return pMergeHead
		

第二种方法循环：

def Merge(self, pHead1, pHead2):
	if pHead1 == None:
		return pHead2
	elif pHead2 == None:
		return pHead1
	if pHead1.val < pHead2.val:
		pMergeHead = plist = pHead1
		pHead1 = pHead1.next
	else:
		pMergeHead = plist = pHead2
		pHead2 = pHead2.next
	
	while pHead1 and pHead2:
		if pHead1.val < pHead2.val:
			plist.next = pHead1
			plist = plist.next
			pHead1 = pHead1.next
		else:
			plist.next = pHead2
			plist = plist.next
			pHead2 = pHead2.next
	if pHead1 != None:
		plist.next = pHead1
	elif pHead2 != None:
		plist.next = pHead2
	return pMergeHead