[leetcode] Rotate List

问题描述：

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.

基本思想：

本题需要考虑k 大于链表长度的情况。所以链表需要右移的数字是 k%size。

代码：

ListNode *rotateRight(ListNode *head, int k) { //C++
if(head ==NULL || k == 0)
return head;

ListNode* tmp = head;
int size = 1;
while(tmp->next != NULL)
{
size++;
tmp = tmp->next;
}
ListNode* final = tmp;

int shift = k%size;
if(shift == 0)
return head;

ListNode* fast = head;
ListNode* pre = head;
for(int i = 0; i< size-shift; i++)
{
pre = fast;
fast = fast->next;

}
final->next = head;
head = fast;
pre->next = NULL;

return head;
}
};