21. 合并两个有序链表

一、Java

class Solution {public ListNode mergeTwoLists(ListNode list1, ListNode list2) {if (list1 == null) return list2;if (list2 == null) return list1;if (list1.val < list2.val) {list1.next = mergeTwoLists(list1.next, list2);return list1;} else {list2.next = mergeTwoLists(list1, list2.next);return list2;}}
}

二、C++

/*** Definition for singly-linked list.* struct ListNode {*     int val;*     ListNode *next;*     ListNode() : val(0), next(nullptr) {}*     ListNode(int x) : val(x), next(nullptr) {}*     ListNode(int x, ListNode *next) : val(x), next(next) {}* };*/
…            return list2;}}
};

三、Python

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:if list1 is None:return list2if list2 is None:return list1if list1.val < list2.val:list1.next = self.mergeTwoLists(list1.next, list2)return list1else:list2.next = self.mergeTwoLists(list1, list2.next)return list2

四、JavaScript

var mergeTwoLists = function(list1, list2) {if (list1 === null) return list2;if (list2 === null) return list1;if (list1.val < list2.val) {list1.next = mergeTwoLists(list1.next, list2);return list1;} else {list2.next = mergeTwoLists(list1, list2.next);return list2;}
};

五、Go

func mergeTwoLists(list1 *ListNode, list2 *ListNode) *ListNode {if list1 == nil {return list2}if list2 == nil {return list1}if list1.Val < list2.Val {list1.Next = mergeTwoLists(list1.Next, list2)return list1} else {list2.Next = mergeTwoLists(list1, list2.Next)return list2}
}