// insdel.cpp: Insert and deletions in a list
#include <string>
#include <iostream>
#include <list>
using namespace std;

void showlist(const string &str, const list<int> &L) {
 list<int>::const_iterator i;
 cout << str << endl << " ";
 for (i = L.begin();  i != L.end(); ++i)
  cout << *i << " ";
  cout << endl;
}

int main() {
 list<int> L;
 int x;
 cout << "Enter positive integers, followed by 0:\n";
 while (cin >> x, x != 0 )
  L.push_back(x);
 showlist("Initial list:", L);
 L.push_front(123);
 showlist("After inserting 123 at the beginning:", L);
 list<int>::iterator i = L.begin();
 L.insert(++i, 456);
 showlist("After inserting 456 at the second position:", L);
 i = L.end();
 L.insert(--i,999);
 showlist("After inserting 999 just before the end:", L);
 i = L.begin(); x = *i;
 L.pop_front();
 cout << "Deleted at the beginning: " << x << endl;
 showlist("After this deletion:", L);
 i = L.end(); x = *--i;
 L.pop_back();
 cout << "Deleted at the end: " << x << endl;
 showlist("After this deletion:", L);
 i = L.begin();
 x = *++i;
 cout << "To be deleted: " << x << endl;
 L.erase(i);
 showlist("After this deletion (of second element):", L);
 return 0;
}