Кольцевой список однозвязный

#include <iostream>
#include <conio.h>
#include <ctime>
struct book
{
    int year;
    book *next;
};
using namespace std;
void Init(book *begin)
{
 
 
    int a[4] = { 12, 42, 221, 552 };
    book *q = begin;
    for (int i = 0; i < 4; i++)
    {
 
        book *t = new book;
        t->year = a[i];
        q->next = t;
        t->next = begin;
        q = t;
 
 
    }
 
 
}
void Print(book *begin)
{
    book *print = begin;
    do
    {
        cout << print->year << ' ';
        print = print->next;
    } while (print != begin);
}
void Add(book *begin,int a)
{
    book *cur = new book;
    book *q = begin;
    cur->year = a;
    book *last = begin;
    while (last->next != begin) 
        last = last->next;// search last element
 
    if (cur->year < begin->year)
    {
        cur->next = begin;
        last->next = cur;
        begin = cur;
    }
            
    
}
void main()
{
    book *begin = NULL;
    book *last = begin;
    if (begin == NULL)
    {
        begin = new book;
        begin->year = 11;
        begin->next = begin;
    }
    Init(begin);
    Add(begin, 1);
    Print(begin);
    _getch();
}

void Add(book *&begin, int a)
{
    book *cur = new book;
    cur->year = a;
    book *sup = begin;
    
    if (cur->year < begin->year)
    {
        while (sup->next != begin)
            sup = sup->next;
        begin = cur;
    }
    else
        while (sup->next->year < cur->year && sup->next != begin)
            sup = sup->next;
 
    cur->next = sup->next;
    sup->next = cur;
}