leecode合并两个有序链表

class Solution:
    def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
        if not l1: return l2  # 终止条件，直到两个链表都空
        if not l2: return l1
        if l1.val <= l2.val:  # 递归调用
            l1.next = self.mergeTwoLists(l1.next,l2)
            return l1          
        else:
            l2.next = self.mergeTwoLists(l1,l2.next)
            return l2

学习链表

class Node:
    def __init__(self,cargo = None, next = None):
        self.cargo = cargo
        self.next = next
    def __str__(self):
        #测试基本功能，输出字符串
        return str(self.cargo)
print(Node("text"))
#输出text
node1 = Node(1)
node2 = Node(2)
node3 = Node(3)
node1.next = node2
node2.next = node3
def printList(node):
    while node:
        print(node)
        node = node.next
printList(node1)