leetcode做题总结，题目Rotate List 2012/03/27

这个题目是链表的循环右移

public ListNode rotateRight(ListNode head, int n) {
        if(head==null)return null;
        if(head.next==null)return head;
        if(n==0)return head;
        int num=1;
        ListNode end=head;
        while (end.next!=null){
            end=end.next;
            num++;
        }
        end.next=head;
        if(num<=n) n=n%num;
        num=num-n-1;
        while(num>0){
            head=head.next;
            num--;
        }
        end = head.next;
        head.next=null;
        return end;
    }

Update 2015/08/20:上面的方法思路没问题，下面的和上面的思路一样

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param head: the List
     * @param k: rotate to the right k places
     * @return: the list after rotation
     */
    public ListNode rotateRight(ListNode head, int k) {
        // write your code here
        if (head == null)
            return null;
        if (k == 0)
            return head;
        int len = 1;
        ListNode a = head;
        while (a.next != null){
            len++;
            a = a.next;
        }
        k = k % len;
        k = len - k;
        a.next = head;
        a = head;
        while (k-- > 1){
            a = a.next;
        }
        head = a.next;
        a.next = null;
        return head;
    }
}