#include <iostream>
using namespace std;

struct p{
        int a;
	p * pNext;
	p * pPrev;
};

int del (int to_delete, p * & pAnker);

int main()
{
	p *pAnchor, *pNew, *pLast;
	int i = 1;
	int tmp;
	
	cout << "Geben Sie 6 Zahlen ein (getrennt durch Leerzeichen): ";
	pAnchor = new p;
	cin >> tmp;
	pAnchor -> a = tmp;
	pAnchor -> pNext = pAnchor -> pPrev = NULL;
	pLast = pAnchor;
	while (i < 6)
	{
		pNew = new p; 
		cin >> tmp;
		pNew -> a = tmp;
		pLast -> pNext = pNew; 
		pNew -> pPrev = pLast;
		pLast = pNew;
		pLast -> pNext = NULL;
		i=i+1;
	}

	cout << "Geben Sie die zu loeschende Zahl ein: ";
	cin >> tmp;
	cout << del(tmp,pAnchor) << " Elemente geloescht!" << endl;

	// alle a-Instanzen von hinten beginnend ausgeben
	// ACHTUNG: pLast koennte durch Loeschen des letzten Elementes
	// ungueltig geworden sein, also manuell pLast aktualisieren
	pLast = pAnchor;
	if(pLast != NULL)
		while(pLast->pNext != NULL)
			pLast = pLast->pNext;
	cout << "Ausgabe von hinten nach Loeschvorgang: ";
	p* pHelp = pLast;
	tmp = 0;
	while(pHelp != NULL)
	{
		cout << pHelp->a << " ";
		pHelp = pHelp->pPrev;
		tmp++;
	}
	if(!tmp)
		cout << "Keine Elemente mehr in der Liste!";
	cout << endl;

	return 0;
}

int del (int to_delete, p * & pAnker)
{
	p *pSearch = pAnker;
	int count_del = 0;

	// Vorkommen von to_delete suchen und loeschen
	while(pSearch != NULL)
	{
		if(pSearch->a == to_delete)
		{
			p *pDelete = pSearch;
			// erstes Element zu loeschen
			if(pDelete->pPrev == NULL){
				pAnker = pDelete->pNext;
				// wenn erstes Element nicht auch letztes
				if(pAnker != NULL)
					pAnker->pPrev = NULL;
			}
			// letztes Element zu loeschen
			else if(pDelete->pNext == NULL){
				pDelete->pPrev->pNext = NULL;
			}
			// Element in der Mitte zu loeschen
			else{
				pDelete->pPrev->pNext = pDelete->pNext;
				pDelete->pNext->pPrev = pDelete->pPrev;
			}
			pSearch = pSearch->pNext;
			delete pDelete;
			count_del++;
		}
		else
			pSearch = pSearch->pNext;
	}

	return count_del;
}