题解 | #合并两个排序的链表#

# 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 not pHead1:
            return pHead2
        if not pHead2:
            return pHead1

        ret = ListNode(0)    # 构造头结点的头,用于记录头
        curr = ret           # 当前节点
        while pHead1 and pHead2:
            if pHead1.val > pHead2.val:
                curr.next = pHead2
                pHead2 = pHead2.next
            else:
                curr.next = pHead1
                pHead1 = pHead1.next
            curr = curr.next  # 向前移动指针
        curr.next = pHead1 if pHead1 else pHead2
        return ret.next