37-Rotate Linked List

/**
 * Definition for singly-linked list.
 * class Node {
 * public:
 *     int data;
 *     Node *next;
 *     Node() : data(0), next(nullptr) {}
 *     Node(int x) : data(x), next(nullptr) {}
 *     Node(int x, Node *next) : data(x), next(next) {}
 * };
 */

Node *rotate(Node *head, int k) {
     // Write your code here.
     //Edge Cases
     if(head==NULL || head->next==NULL || k==0){
          return head;
     }

     //calculate the length while reaching to the end of LL
     Node* curr=head;
     int len=1;
     while(curr->next && ++len){
          curr=curr->next;
     }

     //Now you have the length of the linked list and you are at the last node with curr pointer
     //join the last node to the first node
     curr->next=head;
     k=k%len;
     k=len-k;

     while(k--){
          curr=curr->next;
     }

     //Now you are one before from where we have to roate
     head=curr->next;
     curr->next=NULL;

     return head;

}