题解 | #删除链表的倒数第n个节点#

快慢指针加虚拟头结点处理。注意处理链表长度为n的和小于n的情形。

class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode node(0);
        node.next = head;

        ListNode* fast = head;
        ListNode* slow = &node;

        // fast前进 n步
        for(int i=0; i<n; i++) {
            if(!fast)    return head;
            fast = fast->next;
        }

        while(fast) {
            fast = fast->next;
            slow = slow->next;
        }
        ListNode* temp = slow->next->next;
        delete slow->next;
        slow->next = temp;        

        return node.next;
    }
};