题解 | #牛群旋转#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @param k int整型 
     * @return ListNode类
     */
    ListNode* rotateLeft(ListNode* head, int k) {
        // write code here
        int n = 0;
        ListNode* cur = head;
        while (cur) {
            cur = cur->next;
            n++;
        }
        k = k%n;
        ListNode* fast = head;
        ListNode* slow = head;
        for (int i = 0; i<k; i++) {
            fast = fast->next;
        }
        while (fast->next) {
            fast = fast->next;
            slow = slow->next;
        }
        ListNode* reshead = slow->next;
        fast->next = head;
        slow->next = nullptr;

        return reshead;

    }
};