61. Rotate List (Medium)
https://leetcode.com/problems/rotate-list/
Given a linked list, rotate the list to the right by k places, where k is non-negative.
Example 1:
Input: 1->2->3->4->5->NULL, k = 2 Output: 4->5->1->2->3->NULL Explanation: rotate 1 steps to the right: 5->1->2->3->4->NULL rotate 2 steps to the right: 4->5->1->2->3->NULL
Example 2:
Input: 0->1->2->NULL, k = 4 Output:2->0->1->NULL
Explanation: rotate 1 steps to the right: 2->0->1->NULL rotate 2 steps to the right: 1->2->0->NULL rotate 3 steps to the right:0->1->2->NULL
rotate 4 steps to the right:2->0->1->NULL
Solutions
class Solution {
public ListNode rotateRight(ListNode head, int k) {
if (head == null || head.next == null) {
return head;
}
// For convenience, create a dummy node that doesn't belong to the give ListNode.
ListNode dummy = new ListNode(-1);
dummy.next = head;
ListNode endP = dummy;
ListNode kthP = dummy;
int len;
// Get the total length of the list
for (len = 0; endP.next != null; len++) {
endP = endP.next;
}
// Get the (len - k%len)th node
for (int j = len - (k % len); j > 0; j--) {
kthP = kthP.next;
}
// Rotate the list
endP.next = dummy.next;
dummy.next = kthP.next;
kthP.next = null;
return dummy.next;
}
}