LeetCode 刷题【61. 旋转链表】

61. 旋转链表

自己做

解：截取拼接

/**
 * 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) {
        ListNode *p = head, *q = head, *r = head;
        int l = 0;                          //链表长

        if(head == nullptr || head->next == nullptr)                 //没有移动空间
            return head;

        while(p != nullptr){                //计算链表长
            p = p -> next;
            l++;
        }
        p = head;                           //归位p

        //调整k
        k %= l;

        if(k == 0)                          //为0则不移动
            return head;

        for(int i = 0; i < k; i++)          //q、r包含k个元素
            r = r->next;

        if(k > 0)
            q = p->next;

        while(r->next != nullptr){        //使r指向尾部
            p = q;
            r = r->next;
            q = q->next;
        }

        p->next = nullptr;
        r->next = head;

        return q;

    }
};