Leetcode 21 合并链表(python)

题目描述

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。

方法一（非递归）：

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    # 返回合并后列表
    def Merge(self, pHead1, pHead2):
        first = head = ListNode(0)
        while pHead1 and pHead2:
            if pHead1.val <= pHead2.val:
                head.next = pHead1
                pHead1 = pHead1.next
            else:
                head.next = pHead2
                pHead2 = pHead2.next
            head = head.next
                
        if pHead1:
            head.next = pHead1
        if pHead2:
            head.next = pHead2
                
        return first.next
            

方法二（递归）：

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    # 返回合并后列表
    def Merge(self, pHead1, pHead2):
        if not pHead1:
            return pHead2
        if not pHead2:
            return pHead1
        if pHead1.val <= pHead2.val:
            pHead1.next = self.Merge(pHead1.next, pHead2)
            return pHead1
        else:
            pHead2.next = self.Merge(pHead1, pHead2.next)
            return pHead2
            

-------------------------------------------------------------------------------------------------------------------------------------

更多题目包括leetcode、牛客网、各种排序算法解法参见个人GitHub，持续更新中，欢迎star ~~

https://github.com/PemLer/Journey_of_leetcode

-------------------------------------------------------------------------------------------------------------------------------------