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19. Remove Nth Node From End of List

难度:Medium

刷题内容

原题连接

  • https://leetcode.com/problems/remove-nth-node-from-end-of-list/

内容描述

Given a linked list, remove the n-th node from the end of list and return its head.

Example:

Given linked list: 1->2->3->4->5, and n = 2.

After removing the second node from the end, the linked list becomes 1->2->3->5.

˼· **- ʱ�临�Ӷ�: O(n)*- �ռ临�Ӷ�: O(1)***

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
       ListNode* current = head;
        int num = 0;
        while(current)
        {
            num++;
            current = current ->next;
        }
        ListNode* n1 = new ListNode(0);
        n1 ->next = head;
        current = n1;
        num -= n;
        while(num)
        {
            num--;
            current = current ->next;
        }
        ListNode* temp = current ->next;
        current ->next = temp ->next;
        return n1 ->next;
    }
};


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