19.Remove Nth Node From End of List

Tags: Medium Linked List

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

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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.

Note:

Given n will always be valid.

Follow up:

Could you do this in one pass?

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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 * dummy = new ListNode(0);
        dummy -> next = head;
        ListNode *pre = dummy, *cur = pre -> next, *p = cur;

        for (int i = 1; i <= n; ++i){
            p = p -> next;
        }
        while(p){
            cur = cur -> next;
            pre = pre -> next;
            p = cur;
            for (int i = 1; i <= n; ++i){
                p = p -> next;
            }
        }
        cur = cur -> next;
        pre -> next = cur;

        return dummy -> next;
    }
};