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.

k=2 就是向右移动2次

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* rotateRight(struct ListNode* head, int k) {
    struct ListNode *cur;
    cur = head;
    int n = 1;
    if(head == NULL)
        return NULL;
    while(cur->next != NULL)                 //求链表长度，把cur定位到尾结点
    {
        cur = cur->next;
        n++;
    }
    k = n - k % n;                  //注意K有可能大于链表长度 要取余数
    cur->next = head;
    cur = head;
    k--;
    while(k)                                   //cur移动到断开前的位置
    {
        cur = cur->next;
        k--;
    }
    head = cur->next;
    cur->next = NULL;
    return head;
}