Leetcode: Rotate List
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.
Anaylisis: Linked List题目的做法其实比较固定,就是Runner Technique(Two pointer) 方法加上 Dummy Node(设置一个head之前的虚假节点)两种方法,这道题就这样搞一搞就出来了。
需要注意的是:处理null 输入需要特别考虑,然后,需要找到新的linked list的头
第二遍做法:注意15行需要特别处理,wrap up了之后n=0的情况
1 public class Solution { 2 public ListNode rotateRight(ListNode head, int n) { 3 if (head == null) return null; 4 ListNode dummy = new ListNode(-1); 5 dummy.next = head; 6 ListNode cursor = dummy; 7 ListNode walker = dummy; 8 ListNode runner = dummy; 9 int count = 0; 10 while (cursor.next != null) { 11 cursor = cursor.next; 12 count ++; 13 } 14 n %= count; 15 if (n == 0) return head; 16 while (n > 0) { 17 runner = runner.next; 18 n--; 19 } 20 while (runner.next != null) { 21 runner = runner.next; 22 walker = walker.next; 23 } 24 dummy.next = walker.next; 25 walker.next = runner.next; 26 runner.next = head; 27 return dummy.next; 28 } 29 }