LeetCode - Rotate List

题目：

Given a list, rotate the list to the right by k places, where k is non-negative.

For example:

Given

1->2->3->4->5->NULL

and k =

2

,

return

4->5->1->2->3->NULL

.

思路：

此题和Remove Nth Node from End of List类似，但首先得统计总的个数

package list;

public class RotateList {

public ListNode rotateRight(ListNode head, int k) {
if (k == 0 || head == null) return head;

ListNode x = head;
int count = 0;
while (x != null) {
++count;
x = x.next;
}

int n = k;
if (k >= count) {
if (k % count == 0)
return head;
else
n = k % count;
}

ListNode p = head;
ListNode q = head;
while (p != null && n > 0) {
p = p.next;
--n;
}

while (p.next != null && q.next != null) {
p = p.next;
q = q.next;
}

ListNode newhead = q.next;
p.next = head;
q.next = null;
return newhead;
}

public static void main(String[] args) {
// TODO Auto-generated method stub
RotateList r = new RotateList();
ListNode a1 = new ListNode(1);
ListNode a2 = new ListNode(2);
ListNode a3 = new ListNode(3);
ListNode a4 = new ListNode(4);
ListNode a5 = new ListNode(5);
a1.next = a2;
a2.next = a3;
a3.next = a4;
a4.next = a5;
a5.next = null;
ListNode head = r.rotateRight(a1, 2);
while (head != null) {
System.out.println(head.val);
head = head.next;
}
}

}