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
        // 涉及到删除，头节点可能会发生改动，引入dummy
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        ListNode* fast = dummy;
        ListNode* slow = dummy;
        
        while(n--){
            fast = fast->next;
            if(!fast)
                return nullptr;
        }
        
        // 因为需要删除倒数第k个节点，我们需要找到倒数第k+1个节点
        fast = fast->next;
        
        while(fast){
            fast = fast->next;
            slow = slow->next;
        }
        
        slow->next = slow->next->next;
        
        return dummy->next;
    }
};