61. 旋转链表

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def rotateRight(self, head: ListNode, k: int) -> ListNode:
        if k == 0 or head is None or head.next is None:
            return head
        n, cur = 0, head
        while cur:
            n, cur = n + 1, cur.next
        k %= n
        if k == 0:
            return head
        p = q = head
        for i in range(k):
            q = q.next
        while q.next:
            p, q = p.next, q.next
        start = p.next
        p.next = None
        q.next = head
        return start

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (k == 0 || head == null || head.next == null) {
            return head;
        }
        ListNode cur = head;
        int n = 0;
        while (cur != null) {
            cur = cur.next;
            ++n;
        }
        k %= n;
        if (k == 0) {
            return head;
        }
        ListNode p = head, q = head;
        while (k-- > 0) {
            q = q.next;
        }
        while (q.next != null) {
            p = p.next;
            q = q.next;
        }
        ListNode start = p.next;
        p.next = null;
        q.next = head;
        return start;
    }
}

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int val=0, ListNode next=null) {
 *         this.val = val;
 *         this.next = next;
 *     }
 * }
 */
public class Solution {
    public ListNode RotateRight(ListNode head, int k) {
        if (k == 0 || head == null || head.next == null)
        {
            return head;
        }
        ListNode cur = head;
        var n = 0;
        while (cur != null)
        {
            cur = cur.next;
            ++n;
        }
        k %= n;
        if (k == 0)
        {
            return head;
        }
        ListNode p = head, q = head;
        while (k-- > 0)
        {
            q = q.next;
        }
        while (q.next != null)
        {
            p = p.next;
            q = q.next;
        }
        ListNode start = p.next;
        p.next = null;
        q.next = head;
        return start;

    }
}