找出链表倒数第k个元素-链表题
LCR 140. 训练计划 II - 力扣（LeetCode）
快慢指针。快指针臂慢指针快cnt个元素到最后；
class Solution {
public:ListNode* trainingPlan(ListNode* head, int cnt) {struct ListNode* quick = head;struct ListNode* slow = head;for(int i = 0; i < cnt ; i++){quick = quick->next;}while(quick){quick = quick->next;slow = slow->next;}return slow;}
};