题解 | #合并两个排序的链表#(哨兵+双指针)

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param pHead1 ListNode类 
# @param pHead2 ListNode类 
# @return ListNode类
#
class Solution:
    def Merge(self , pHead1: ListNode, pHead2: ListNode) -> ListNode:
        # write code here
        if pHead1 ==None:
            return pHead2
        elif pHead2 ==None:
            return pHead1

        head = ListNode(0)
        res = head

        while pHead1 and pHead2:
            if pHead1.val < pHead2.val:
                res.next = pHead1
                pHead1 = pHead1.next
            else:
                res.next = pHead2
                pHead2 = pHead2.next
            res = res.next
        
        if pHead1 !=None:
            res.next = pHead1
        if pHead2 !=None:
            res.next = pHead2

        return head.next