[OJ.leetcode] rotate-list

https://oj.leetcode.com/problems/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. 

  /** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ /* k=2 1->2->3->4->5 . . 1->2->3->4->5 . . 4->5->1->2->3 k=4; 1->2->3->4->5 . . 2->3->4->5->1 k=5; 1->2->3->4->5 .. //if first==second then return head k=7(same as k=2); 1->2->3->4->5 . . 4->5->1->2>3 test cases {}, 0 {1}, 1 {1,2}, 1 {1,2}, 2 {1,2}, 3 */ class Solution { public: ListNode *rotateRight(ListNode *head, int k) { if(k <=0 || head == NULL) return head; ListNode* first = head; ListNode* second = head; //shift k nodes for(int i=0; i<k ; i++) { second = second->next; if(second == NULL) { k -= i; i = 0; second = head; } } if(head == second) return head; while(second->next) { first = first->next; second = second->next; } second->next = head; head = first->next; first->next = NULL; return head; } };