[leetcode] 19. Delete the penultimate node of the linked list

19.、 Delete the last of the linked list N Nodes

subject ：

I'll give you a list , Delete the last of the linked list n Nodes , And return the head node of the list .

Example 1：

 Input ：head = [1,2,3,4,5], n = 2
 Output ：[1,2,3,5]

Example 2：

 Input ：head = [1], n = 1
 Output ：[]

Example 3：

 Input ：head = [1,2], n = 1
 Output ：[1]

Tips ：

The number of nodes in the list is sz
1 <= sz <= 30
0 <= Node.val <= 100
1 <= n <= sz

Their thinking ：

This question LeetCode The difficulty of evaluation is medium , I think this question is simpler than the simple one .

Why do you say that ？

The linked list deletes a node at a certain position , Is it difficult ？

You can find rules . Because it is required to delete the penultimate n Nodes

The official solution is to calculate the length of the linked list 、 Stack and double pointer .

Here is a new idea , recursive ！ Find the length of the deleted location linked list .

Simple and crude

Specific code ：

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */
class Solution {
    
        int i=0;
    public ListNode removeNthFromEnd(ListNode head, int n) {
    
             if(head.next!=null)
            head.next=removeNthFromEnd(head.next,n);
        i++;
        if(i==n)
            return head.next;
        else return head;
    }
}