LeetCode rotate-list

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。 示例 1:

输入: 1->2->3->4->5->NULL, k = 2 输出: 4->5->1->2->3->NULL 解释: 向右旋转 1 步: 5->1->2->3->4->NULL 向右旋转 2 步: 4->5->1->2->3->NULL

示例 2:

输入: 0->1->2->NULL, k = 4 输出: 2->0->1->NULL 解释: 向右旋转 1 步: 2->0->1->NULL 向右旋转 2 步: 1->2->0->NULL 向右旋转 3 步: 0->1->2->NULL 向右旋转 4 步: 2->0->1->NULL

解答:

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/**
* 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) {
int len = 0;
ListNode* tmp = head;
ListNode* last = nullptr;

while (tmp) {
++len;
last = tmp;
tmp = tmp->next;
}

if (len == 0) return head;
k = k % len;
last->next = head;
tmp = head;
for (int i = 0; i < len - k - 1; ++i) {
tmp = tmp->next;
}
head = tmp->next;
tmp->next = nullptr;
return head;
}
};

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