Start by iterating to the end of the Circular Linked List (CLL).
Make the next pointer of the last node point to the newNode.
Make the next pointer of the newNode point to the head node, establishing a circular connection.
Return the newNode as the head of the updated CLL.

Code

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

// define node structure
struct node {
  // store data
  int data;
  // store next pointer
  node* next;
  // initialize node
  node(int d) { data = d; next = NULL; }
};

// insert at beginning in circular linked list (O(n))
node* insertion_beg(node* head, int x) {
  // create new node
  node* newnode = new node(x);
  // handle empty list
  if (head == NULL) {
    // point to itself to form single-node circle
    newnode->next = newnode;
    // return new head
    return newnode;
  } else {
    // start at head to find last node
    node* current = head;
    // move until current->next is head
    while (current->next != head) {
      current = current->next;
    }
    // link new node to old head
    newnode->next = current->next;
    // close circle by pointing last to new node
    current->next = newnode;
    // new node becomes head
    return newnode;
  }
}

// print circular linked list once around the circle
void printCLL(node* head) {
  // start traversal cursor
  node* current = head;
  // 