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->NULLExplanation: 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->NULLrotate 4 steps to the right:2->0->1->NULL
代码：
/**
* 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) return NULL;
ListNode* root = head;
int len = 0;
while(root) {
root = root -> next;
len ++;
}
k = k % len;
if(k == 0) return head;
ListNode* slow = head;
ListNode* fast = head;
for(int i = 0; i < k; i ++) {
if(fast) fast = fast -> next;
}
if(!fast) return head;
while(fast -> next) {
slow = slow -> next;
fast = fast -> next;
}
fast -> next = head;
fast = slow -> next;
slow -> next = NULL;
return fast;
}
};
要注意 k 的处理要 k % len 但是后面把两部分拼接的三句话不是很懂 :-(