Rotate_LinkList.cpp

// Problem: Given the head of a linked list, rotate the list to the right by k places.

// Input:
// 	head = [1,2,3,4,5] 
// 	k = 2
// Output:
//  head = [4,5,1,2,3]



//code
#include<bits/stdc++.h>
using namespace std;

class node {
    public:
        int num;
        node* next;
        node(int a) {
            num = a;
            next = NULL;
        }
};
//utility function to insert node at the end of the list
void insertNode(node* &head,int val) {
    node* newNode = new node(val);
    if(head == NULL) {
        head = newNode;
        return;
    }
    node* temp = head;
    while(temp->next != NULL) temp = temp->next;

    temp->next = newNode;
    return;
}
//utility function to rotate list by k times
node* rotateRight(node* head,int k) {
    if(head == NULL||head->next == NULL) return head;
    for(int i=0;i<k;i++) {
        node* temp = head;
        while(temp->next->next != NULL) temp = temp->next;
        node* end = temp->next;
        temp->next = NULL;
        end->next = head;
        head = end;
    }
    return head;
}
//utility function to print list
void printList(node* head) {
    while(head->next != NULL) {
        cout<<head->num<<"->";
        head = head->next;
    } 
    cout<<head->num<<endl;
    return;
}

int main() {
    node* head = NULL;
    //inserting Node
    insertNode(head,1);
    insertNode(head,2);
    insertNode(head,3);
    insertNode(head,4);
    insertNode(head,5);

    cout<<"Original list: ";
    printList(head);

    int k = 2;
    node* newHead = rotateRight(head,k);//calling function for rotating right of 
    the nodes by k times

    cout<<"After "<<k<<" iterations: ";
    printList(newHead);//list after rotating nodes
    return 0;
}