leetcode21

/*** Definition for singly-linked list.* public class ListNode {*     public int val;*     public ListNode next;*     public ListNode(int x) { val = x; }* }*/
public class Solution {public ListNode MergeTwoLists(ListNode l1, ListNode l2) {//递归实现链表合并ListNode l = null;if (l1 == null && l2 != null){return l2;}else if (l2 == null && l1 != null){return l1;}else if (l1 == null && l2 == null){return null;}else{if (l1.val < l2.val){if (l == null){l = l1;}l.next = MergeTwoLists(l1.next, l2);}else{if (l == null){l = l2;}l.next = MergeTwoLists(l1, l2.next);}return l;}}
}

https://leetcode.com/problems/merge-two-sorted-lists/#/description

 

补充一个python的实现：

class Solution:
    def mergeTwoLists(self, l1: 'ListNode', l2: 'ListNode') -> 'ListNode':
        if l1 == None:
            return l2
        if l2 == None:
            return l1
        if l1.val < l2.val:
            l1.next = self.mergeTwoLists(l1.next,l2)
            return l1
        else:
            l2.next = self.mergeTwoLists(l2.next,l1)
            return l2