[LeetCode] 61 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.

解题思路：

双指针（tail，pre）找到链表的尾部和总长度，使用pre走 （len-k%(len)-1) 长度到达要修改的尾部点进行修改

/**

 * Definition for singly-linked list.

 * struct ListNode {

 *     int val;

 *     ListNode *next;

 *     ListNode(int x) : val(x), next(NULL) {}

 * };

 */

class Solution {

public:

    ListNode *rotateRight(ListNode *head, int k) {

        if(head==NULL||head->next==NULL)return head;

        ListNode *tail,*pre;

        tail=pre=head;

        int len=1;

        while(tail->next!=NULL) //找到尾部

        {

            tail=tail->next;

            len++;

        }

        int i=len-(k%(len))-1;  //考虑k数据的过大

        while(i>0)

        {

            i--;

            pre=pre->next;

        }

        tail->next=head;

        head=pre->next;

        pre->next=NULL;

        return head;

    }

};