. - 力扣（LeetCode）

class Solution {
public:
    ListNode* trainningPlan(ListNode* head, int cnt) {
        int n = 0;
        ListNode* node = nullptr;

        for (node = head; node; node = node->next) {
            n++;
        }
        for (node = head; n > cnt; n--) {
            node = node->next;
        }
      
        return node;
    }
};

class Solution {
public:
    ListNode* trainningPlan(ListNode* head, int cnt) {
        ListNode* fast = head;
        ListNode* slow = head;

        while (fast && cnt > 0) {
            fast = fast->next;
            cnt--;
        }
        while (fast) {
            fast = fast->next;
            slow = slow->next;
        }

        return slow;
    }
};