61. Rotate List

Posted 2022-06-25 forprometheus-jun

description:

Given a linked list, rotate the list to the right by k places, where k is non-negative.
Note:

Example:

Example 1:

Input: 1->2->3->4->5->NULL, k = 2
Output: 4->5->1->2->3->NULL
Explanation:
rotate 1 steps to the right: 5->1->2->3->4->NULL
rotate 2 steps to the right: 4->5->1->2->3->NULL

Example 2:

Input: 0->1->2->NULL, k = 4
Output: 2->0->1->NULL
Explanation:
rotate 1 steps to the right: 2->0->1->NULL
rotate 2 steps to the right: 1->2->0->NULL
rotate 3 steps to the right: 0->1->2->NULL
rotate 4 steps to the right: 2->0->1->NULL

answer:

/**
 * 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) return NULL;
        ListNode* cur = head;
        int n = 1;
        while(cur->next)
            n++;
            cur = cur->next;
        
        cur ->next = head;
        int m = n - k%n;
        for (int i = 0; i < m; ++i) 
            cur = cur->next;
        
        ListNode *newhead = cur -> next;
        cur->next = NULL;
        return newhead;
    
;

relative point get√：

hint :