【2024考研】题解8 | #删除链表的倒数第n个节点#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
#include <cstddef>
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @param n int整型 
     * @return ListNode类
     */
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        // write code here
        //为空直接返回
        if(head == NULL) return head;
        //来一个新表头防止第一个节点被删后没有返回值
        ListNode *mxy = new ListNode(0);
        mxy->next = head;
        head = mxy;

        //快慢指针
        ListNode *fast = head;
        ListNode *slow = head;
        //快指针定好长度
        for(int i = 0; i < n; i++){
            fast = fast->next;
        }
        //快慢指针同步移动，slow指针定位所需要删除的节点
        while(fast->next != NULL){
            slow = slow->next;
            fast = fast->next;
        }
        //常规删除 一跨连二跨
        ListNode *temp = slow->next;
        slow->next = slow->next->next;
        delete temp;

        return mxy->next;
        
    }
};