Sytruktur Data: SIngle Linked List Circular

  #include <iostream>
  #include <stdlib.h>
  using namespace std;
struct Data {
  int nilai;
  Data *next;
  };
  Data *head;
void awal(){
  head=NULL;
  }
  bool isEmpty(){
  if (head==NULL)
  return true;
  return false;
  }
  void tambahDataDepan(int dataBaru) {
  Data *baru;
  baru=(Data*) malloc(sizeof(Data));
  baru->nilai=dataBaru;
  baru->next=baru;
  if (isEmpty()){
  head=baru;
  head->next=head;
  } else {
  Data *bantu;
  bantu=head;
  while (bantu->next!=head){
  bantu=bantu->next;
  }
  baru->next=head;
  head=baru;
  bantu->next=head;
  }
  }
  void tambahDataBelakang(int dataBaru){
  Data *baru;
  baru=(Data*) malloc(sizeof(Data));
  baru->nilai=dataBaru;
  baru->next=baru;
  if (isEmpty()){
  head=baru;
  head->next=head;
  } else {
  Data *bantu;
  bantu=head;
  while (bantu->next!=head){
  bantu=bantu->next;
  }
  bantu->next=baru;
  baru->next=head;
  //head=baru;
  //bantu->next=baru;
  }
  }
  void hapusDepan(){
  if(!isEmpty()){
  if(head->next!=head){
  Data *hapus;
  hapus=head;
  Data *bantu;
  bantu=head;
  while (bantu->next!=head){
  bantu=bantu->next;
  }
  bantu->next=head->next;
  head=head->next;
  delete hapus;
  }
  else {
  awal();
  }
  }
  }
  void hapusBelakang(){/* 
  tambah kode program di sini.... 
*/
}
  void cetak(){
  if (!isEmpty()){
  Data *bantu;
  bantu=head;
  do {
  cout<<bantu->nilai<<" ";
  bantu=bantu->next;
  } while(bantu!=head);
 }
  }
  int main(){
  awal();
  tambahDataBelakang(5);
  tambahDataDepan(7);
  tambahDataBelakang(17);
  hapusDepan();
  hapusDepan();
  cetak();
  return 0;
  }