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
#
import bisect
class Solution:
    def Merge(self , pHead1: ListNode, pHead2: ListNode) -> ListNode:
        # write code here
        #法1：将两个列表统一放到一个列表中，边插入边排序
        # sort_list = list()
        # while pHead1:
        #     bisect.insort_left(sort_list,pHead1.val)
        #     pHead1 = pHead1.next
        # while pHead2:
        #     bisect.insort_left(sort_list,pHead2.val)
        #     pHead2 = pHead2.next
        
        # phead3 = ListNode(0)#虚拟头结点
        # cur = phead3
        # for num in sort_list:
        #     cur.next = ListNode(num)
        #     cur = cur.next
        # return phead3.next

        #法2：只用一个直接创建一个链表，边插入边比较
        if not pHead1 and not pHead2:
            return None
        elif not pHead1:
            return pHead2
        elif not pHead2:
            return pHead1
        head = ListNode(0)
        cur = head

        while pHead1 and pHead2:
            if pHead1.val > pHead2.val:
                cur.next=ListNode(pHead2.val)
                cur=cur.next
                pHead2 = pHead2.next
            else:
                cur.next = ListNode(pHead1.val)
                cur = cur.next
                pHead1 = pHead1.next
        if  pHead1:
            cur.next = pHead1
        elif  pHead2:
            cur.next = pHead2
        return head.next