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:
        # special cases
        # both empty
        if not pHead1 and not pHead2:
            return
        if not pHead1 and pHead2:
            return pHead2
        if pHead1 and not pHead2:
            return pHead1

        dummy = None
        cur = None
        if pHead1.val > pHead2.val:
            cur = pHead2
            dummy = cur
            pHead2 = pHead2.next
        else:
            cur = pHead1
            dummy = cur
            pHead1 = pHead1.next

        while pHead1 and pHead2:
            if pHead1.val < pHead2.val:
                cur.next = pHead1
                cur = pHead1
                pHead1 = pHead1.next
            else:
                cur.next = pHead2
                cur = pHead2
                pHead2 = pHead2.next

        if not pHead1:
            cur.next = pHead2
        else:
            cur.next = pHead1

        return dummy