两个队列实现一个栈

class Stack
{
public:
void push(const int& x)
{
_qu1.push(x);
}

void pop()
{
if (_qu1.empty())
{
cout << "empty stack!"<<endl;
return;
}

while (_qu1.size() - 1)
{
_qu2.push(_qu1.front());
_qu1.pop();
}

_qu1.pop();

if (_qu1.empty())
{
while (!_qu2.empty())
{
_qu1.push(_qu2.front());
_qu2.pop();
}
}
else
{
assert(false);
}
}

void print()
{
queue<int> tmp1 = _qu1;
queue<int> tmp2= _qu2;

while (tmp1.size())
{
while (tmp1.size() - 1)
{
tmp2.push(tmp1.front());
tmp1.pop();
}
cout << tmp1.front() << "->";
tmp1.pop();

if (tmp1.empty())
{
while (!tmp2.empty())
{
tmp1.push(tmp2.front());
tmp2.pop();
}
}
else
{
assert(false);
}
}
cout << endl;
}
private:
queue<int> _qu1;
queue<int> _qu2;
};