140.训练计划2

给定一个头节点为 head 的链表用于记录一系列核心肌群训练项目编号，请查找并返回倒数第 cnt 个训练项目编号。

示例 1：

输入：head = [2,4,7,8], cnt = 1
输出：8

提示：

• 1 <= head.length <= 100
• 0 <= head[i] <= 100
• 1 <= cnt <= head.length

代码：

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* trainingPlan(ListNode* head, int cnt) {
        ListNode *per = head, *cut = head;
        for (int i = 0; i < cnt; i++) {
            cut = cut->next;
        }
        while (cut != nullptr) {
            per = per->next;
            cut = cut->next;
        }
        return per;
    }
};