[LeetCode] 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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 Linked List Two Pointers

 

class Solution {
    public:
        ListNode *rotateRight(ListNode *head, int k)
        {
            if(head == NULL) return NULL;
            ListNode * p = head;
            int len = 0;

            ListNode * seg1Last = NULL;
            ListNode * seg2Last = NULL;
            ListNode * seg2Head = NULL;

            while(p != NULL)
            {
                if(p-> next == NULL)
                    seg2Last = p;
                len ++;
                p = p->next;
            }
            k = k % len;
            if(k == 0)
                return head;
            k = len - k;

            p = head;
            while(--k)
            {
                p = p->next;
            }
            seg1Last = p;
            seg2Head = p -> next;

            seg2Last -> next = head;
            seg1Last -> next = NULL;

            return seg2Head;

        }
};