19. 删除链表的倒数第 N 个结点 C++（快慢指针）

19. 删除链表的倒数第 N 个结点
    
    

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int N) {
        ListNode* fast = head;
        ListNode* slow = head;
        for(int i = 0;i<N;i++){
            fast = fast->next;
        }
        while(true){
            if(fast == nullptr){
                return head->next;
            }else if(fast->next == nullptr){
                slow->next = slow->next->next;
                return head;
            }
            slow = slow->next;
            fast = fast->next;
        }
    }
};
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