61. 旋转链表

61. 旋转链表

/**
 * 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* rotateRight(ListNode* head, int k) {
        if(!head)
            return nullptr;
        int length = 0;
        ListNode* point = head;
        ListNode* tail = nullptr;
        while(point)
        {
            ++length;
            tail = point;
            point = point->next;
        }
        k %= length;
        if(!k)
            return head;
        k = length - k - 1;
        point = head;
        for(int i = 0; i < k; ++i)
        {
            point = point->next;
        }
        auto ret = point->next;
        point->next = nullptr;
        tail->next = head;
        return ret;
    }
};