22.链表中倒数第k个节点 (Easy)*

class Solution {
public:
    ListNode* getKthFromEnd(ListNode* head, int k) {
        if(head == nullptr) {
            return nullptr;
        }
        ListNode *fast = head, *slow = head;
        while(k--) {
            fast = fast->next;
        }
        if(fast == nullptr) {
            return head;
        }
        while(fast != nullptr) {
            fast = fast->next;
            slow = slow->next;
        }
        return slow;
    }
};