题解 | #删除链表的倒数第n个节点#

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 * };
 */

class Solution {
  public:
    /**
     *
     * @param head ListNode类
     * @param n int整型
     * @return ListNode类
     */
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        // write code here
        ListNode* dummy = new ListNode(-1);
        dummy->next = head;
        ListNode* slow = dummy, *fast = dummy;
        ListNode* pre = dummy;
        // 1->2->3 2
	  // 倒数第几个，就让fast先走几步
        while (n > 0) {
            fast = fast->next;
            --n;
        }
	  // fast走到空节点时，slow走到倒数第n个
        while (fast != nullptr) {
            pre = slow;
            slow = slow->next;
            fast = fast->next;
        }
        pre->next = slow->next;
        return dummy->next;
    }
};