leetcode删除倒数第n个

Question

leetcode上删除链表的倒数第n个，这样写有啥错误吗，为啥把5给删了；

class Solution {
public:
    int getlength(ListNode* head){
    int length=0;
    while(head){
        length++;
        head=head->next;
    }
    return length;
    }
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        int length=getlength(head);
        ListNode*pre=head;
        for(int i=1;i<length-n+1;i++){
            pre=pre->next;
        }
        pre->next=pre->next->next;
        return head;
    }
};

Answer 1

你调试一下啊，length是多少呢