[LeetCode]Remove Nth Node From End of List

题目描述:(链接)

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

For 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.
Try to do this in one pass.

解题思路:

class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode dummy(-1);
        dummy.next = head;
        ListNode *fast = &dummy;
        ListNode *slow = &dummy;
        
        for (int i = 0; i < n ; ++i) {
            fast = fast->next;
        }
        
        while (fast->next != nullptr) {
            slow = slow->next;
            fast = fast->next;
        }
        
        // ListNode *tmp = slow->next;
        slow->next = slow->next->next;
        // delete tmp;
        
        return dummy.next;
    }
};