旋转链表 使用vector压栈，倒着找到新的链表头，然后循环一把 - lifengyu360/lifengyu_first_git_test GitHub Wiki

给定一个链表，旋转链表，将链表每个节点向右移动 k 个位置，其中 k 是非负数。 /**

• Definition for singly-linked list.
• struct ListNode {

• int val;
  

• ListNode *next;
  

• ListNode() : val(0), next(nullptr) {}
  

• ListNode(int x) : val(x), next(nullptr) {}
  

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

• };

*/

class Solution {

public:

ListNode* rotateRight(ListNode* head, int k) {
    if ( head == nullptr 
         || (k == 0) 
         || (head->next == nullptr)) {
        return head;
    }
    ListNode *tail = head;
    int total = 1;
    while (tail->next){
        total++;
        tail = tail->next;
    }
    tail->next = head;

    k = k%total;
    int num = total - k;//3
    if (num == 0){
        return head;
    }

    ListNode *tmp = head;
    ListNode *tmp_pre = nullptr;
    while (num > 0 ){
        tmp_pre = tmp;
        tmp = tmp->next;
        num--; 
    }

    tmp_pre->next = NULL;
    return tmp;
}

};