leetcode-top100链表专题二

21.合并两个有序链表

题目链接

21. 合并两个有序链表 - 力扣（LeetCode）

解题代码

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

2.两数相加

题目链接

2. 两数相加 - 力扣（LeetCode）

解题思路

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
        if not l1: return l2
        if not l2: return l1

        l1.val += l2.val
        if l1.val >= 10:
            l1.next = self.addTwoNumbers(ListNode(l1.val // 10),l1.next)
            l1.val %= 10

        l1.next = self.addTwoNumbers(l1.next,l2.next)

        return l1