19.删除链表的倒数第N个节点

https://leetcode.cn/problems/remove-nth-node-from-end-of-list/description/

思路

快慢指针

code

/**
 * 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* dummyNode = new ListNode(0);
        dummyNode->next =head;
        ListNode* fast=dummyNode;
        ListNode* slow=dummyNode;

        while(n--){
            fast=fast->next;
        }
        while(fast->next){
            fast=fast->next;
            slow=slow->next;
        }
        ListNode* tmp=slow->next;
        slow->next=slow->next->next;
        delete tmp;
        return dummyNode->next;
    }
};
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