lw65 - original

#include "pt4.h"
#include <fstream>
using namespace std;

struct TList {
    PNode Current;
};

typedef TList* PList;

PNode GetCurrent(PList list);

void SetCurrent(PList list, PNode current);

PNode MoveToFirst(PList list);

PNode MoveToLast(PList list);

bool IsStandalone(PNode current);

void DeleteCurrent(PList list);

void Solve()
{
    Task("ListWork65");

    PNode first;
    pt >> first;

    string fileName;
    pt >> fileName;

    ofstream file(fileName);

    PList list = new TList;
    SetCurrent(list, first);

    PNode current;
    bool goToLast = true;

    while (GetCurrent(list) != NULL) {
        current = goToLast ? MoveToLast(list) : MoveToFirst(list);

        file << current->Data;
        if (!IsStandalone(current))
            file << ' ';

        DeleteCurrent(list);
        goToLast = !goToLast;
    }

    file.close();
}

PNode GetCurrent(PList list) {
    return list->Current;
}

void SetCurrent(PList list, PNode current) {
    list->Current = current;
}

PNode MoveToFirst(PList list) {
    PNode current = GetCurrent(list);
    while (current->Prev != NULL)
        current = current->Prev;

    SetCurrent(list, current);
    return current;
}

PNode MoveToLast(PList list) {
    PNode current = GetCurrent(list);
    while (current->Next != NULL)
        current = current->Next;

    SetCurrent(list, current);
    return current;
}

bool IsStandalone(PNode current) {
    return current->Next == NULL && current->Prev == NULL;
}

void DeleteCurrent(PList list) {
    PNode current = list->Current;
    if (current == NULL)
        return;

    PNode prev = current->Prev;
    PNode next = current->Next;

    if (prev != NULL)
        prev->Next = next;

    if (next != NULL)
        next->Prev = prev;

    delete current;

    SetCurrent(list, prev != NULL ? prev : next);
}