【栈队列】一个数组实现两个栈(共享栈)

template<class T>
class SharedStack
{
public:
SharedStack()
: _a(NULL)
, _top1(0)
, _top2(0)
, _capacity(0)
{
_CheckCapacity();
}
~SharedStack()
{
if (_a)
delete[] _a;
}
void Push1(const T& data)
{
_CheckCapacity();
_a[_top1++] = data;
}
void Push2(const T& data)
{
_CheckCapacity();
_a[_top2--] = data;
}
void Pop1()
{
if (_top1 > 0)
--_top1;
}
void Pop2()
{
if (_top2 < _capacity - 1)
_top2++;
}
size_t Size1()
{
return _top1;
}
size_t Size2()
{
return _capacity - 1 - _top2;
}
bool Empty1()
{
return _top1 == 0;
}
bool Empty2()
{
return _top2 == _capacity - 1;
}
T& Top1()
{
if (_top1>0)
{
return _a[_top1 - 1];
}
}
T& Top2()
{
if (_top2 < _capacity - 1)
return _a[_top2 + 1];
}
private:
//判断
void _CheckCapacity()
{
if (_a == NULL)
{
_capacity += 3;
_a = new T[_capacity];
_top2 = _capacity - 1;
return;
}
if (_top1 == _top2)
{
size_t OldCapacity = _capacity;
_capacity = _capacity * 2;
T* tmp = new T[_capacity];
for (size_t i = 0; i < _top1; i++)
{
tmp[i] = _a[i];
}
for (size_t j = OldCapacity - 1, i = _capacity - 1; j>_top2; j--, i--)
{
tmp[i] = _a[j];
}
delete[] _a;
_a = tmp;
_top2 += _capacity / 2;
}
}
private:
T* _a;
size_t _top1;
size_t _top2;
size_t _capacity;
};