LeetCode 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.

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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) {        if (head == NULL) {            return head;        }        ListNode* newHead = head;        ListNode* cur = head;        ListNode* last;        int n = 0;        while(cur != NULL) {            last = cur;            cur = cur->next;            ++n;        }        k = k % n;        if (k == 0) {            return head;        }        ListNode* pre;        for (int i = n; i > k; --i) {            pre = newHead;            newHead = newHead->next;        }        pre->next = NULL;        last->next = head;        return newHead;    }};