快慢指针思路

快指针抢跑n个节点

class Solution {
public:
    /**
     * 
     * @param head ListNode类 
     * @param n int整型 
     * @return ListNode类
     */
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        // write code here
        ListNode* newList = new ListNode(-1);
        newList->next = head;
        ListNode* cur = head;
        ListNode* pre = newList;
        ListNode* fast = head;
        while(n--){
            fast = fast->next;
        }
        while(fast){
            fast = fast->next;
            pre = cur;
            cur = cur->next;
        }
        pre->next = cur->next;
        return newList->next;
    }
};