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

.

自己在纸上画图，看看指针的变化，注意指针的赋值顺序。

/**
* 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) return head;

int len = 0;
ListNode *testhead = head;
while(testhead != NULL) {
testhead = testhead->next;
len ++;
}

k = k - (k / len) * len;
if(k == 0) return head;

ListNode *cur = head;
for(int ii = 0; ii < k; ii ++) {
cur = cur->next;
}

ListNode *newHead = head;
while(cur->next != NULL) {
cur = cur->next;
newHead = newHead->next;
}

ListNode *newTail = newHead;
newHead = newHead->next;
cur->next = head;
newTail->next = NULL;
return newHead;
}
};