#include <stdexcept>
#include <iostream>
#include <list>
class TrainComposition
{
private:
std::list<int> trains;
public:
void attachWagonFromLeft(int wagonId)
{
trains.push_front(wagonId);
}
void attachWagonFromRight(int wagonId)
{
trains.push_back(wagonId);
}
int detachWagonFromLeft()
{
if (trains.size() == 0)
return NULL;
auto temp = trains.front();
trains.pop_front();
return temp;
}
int detachWagonFromRight()
{
if (trains.size() == 0)
return NULL;
auto temp = trains.back();
trains.pop_back();
return temp;
}
};
#ifndef RunTests
int main()
{
TrainComposition tree;
tree.attachWagonFromLeft(7);
tree.attachWagonFromLeft(13);
std::cout << tree.detachWagonFromRight() << "\n"; // 7
std::cout << tree.detachWagonFromLeft(); // 13
return EXIT_SUCCESS;
}
#endif
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