vector.push_back使用添加对象指针但不添加对象

Question

我正在尝试使用一组固定长度的子堆栈来实现堆栈。对于子堆栈，我使用在构造函数中初始化的固定长度的简单数组。对于堆栈，我使用子堆栈向量。

下面的push方法尝试将内存分配给新的子包并将其推送到向量。但是每当发生新的推送时（让我们在向量setofstacks [1]上说），之前的setofstacks [0]会被调用的substack析构函数获取垃圾值。不知道为什么会发生这种情况。

substack<T> *s = new substack<T>(size);
setofstacks.push_back(*s);
setofstacks[currStackIndex].push(elem);

vector<substack<T>*> setofstacks;

另一方面，如果我将对象转换为子包的对象指针并将其存储在向量中，那么效果非常好。

setofstacks.push_back(new substack<T>(size));
setofstacks[currStackIndex]->push(elem);

/*  Program: Implement a stack of substacks of fixed size
*
*   Date: 12/28/2015
*/

#include <iostream>
#include <vector>

using namespace std;

template <class T>
class substack
{
private:
    T *arr;
    int nextAvailable;
    int size;
public:
    substack(int capacity);
    ~substack();
    void push(T elem);
    T pop();
    T peek();
    bool isfull();
    bool isempty();
};

// Constructor initializing size of substack
template <class T>
substack<T>::substack(int capacity)
{
    nextAvailable = 0;
    size = capacity;
    arr = new T[capacity];
}

// Destructor freeing memory allocated by the stack implemented using array
template <class T>
substack<T>::~substack()
{
    delete[] arr;
    arr = NULL;
}

// Pushing an element on top of a substack of fixed size
template <class T>
void substack<T>::push(T elem)
{
    if (nextAvailable < size)
    {
        arr[nextAvailable] = elem;
        nextAvailable++;
    }
    else
    {
        cout << "Substack is full" << endl;
        return;
    }
}

// Popping the top element from a stack of fixed size
template <class T>
T substack<T>::pop()
{
    nextAvailable--;

    if (nextAvailable >= 0)
    {
        T del = arr[nextAvailable];
        arr[nextAvailable] = NULL;
        return del;
    }
    else
    {
        cout << "Stack is empty" << endl;
        return NULL;
    }
}

// Peeking the top element from a stack of fixed size
template <class T>
T substack<T>::peek()
{
    if (nextAvailable > 0)
    {
        return arr[nextAvailable - 1];
    }
    else
    {
        cout << "Stack is empty" << endl;
        return NULL;
    }
}

// Checking if a substack is full or not
template <class T>
bool substack<T>::isfull()
{
    return (nextAvailable == size);
}

// Checking if a substack is empty or not
template <class T>
bool substack<T>::isempty()
{
    return (nextAvailable == 0);
}

template <class T>
class SetOfStacks
{
private:
    //vector<substack<T>*> setofstacks;
    vector<substack<T>> setofstacks;
    int currStackIndex;
    int size;
public:
    SetOfStacks(int capacity);
    ~SetOfStacks();
    void push(T elem);
    T pop();
    T peek();
};

// Constructor initializing a set of stacks
template <class T>
SetOfStacks<T>::SetOfStacks(int maxStackCapacity)
{
    currStackIndex = 0;
    size = maxStackCapacity;
    substack<T> *s = new substack<T>(maxStackCapacity);
    setofstacks.push_back(*s);
    //setofstacks.push_back(new substack<T>(maxStackCapacity));
}

// Destructor clearing set of stacks vector
template <class T>
SetOfStacks<T>::~SetOfStacks()
{
    setofstacks.clear();
}

// Pushing an element on top of a stack implemented by a set of fixed length substacks
    template <class T>
    void SetOfStacks<T>::push(T elem)
    {
        if (!setofstacks[currStackIndex].isfull())
        {
            setofstacks[currStackIndex].push(elem);
        }
        else
        {
            currStackIndex++;
            substack<T> *s = new substack<T>(size);
            setofstacks.push_back(*s);
            //setofstacks.push_back(new substack<T>(size));
            setofstacks[currStackIndex].push(elem);
        }
    }

// Popping an element from top of a stack implemented by a set of fixed length substacks
template <class T>
T SetOfStacks<T>::pop()
{
    if (!setofstacks[currStackIndex].isempty())
    {
        return setofstacks[currStackIndex].pop();
    }
    else
    {
        setofstacks.pop_back();
        currStackIndex--;

        if (currStackIndex >= 0)
        {
            return setofstacks[currStackIndex].pop();
        }
        else
        {
            cout << "Stack is empty" << endl;
            return NULL;
        }
    }
}

// Peeking an element from top of a stack implemented by a set of fixed length substacks
template <class T>
T SetOfStacks<T>::peek()
{
    return setofstacks[currStackIndex].peek();
}

int main()
{
    SetOfStacks<int> *s = new SetOfStacks<int>(5);
    s->push(1);
    s->push(2);
    s->push(3);
    s->push(4);
    s->push(5);

    s->push(6);
    s->push(7);
    s->push(8);

    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;

    s->push(1);
    s->push(2);
    s->push(3);

    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    //cout << s->pop() << endl;

    system("pause");
}

无法使用完整代码

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Press any key to continue . . .

输出

/*  Program: Implement a stack of substacks of fixed size
*
*   Date: 12/28/2015
*/

#include <iostream>
#include <vector>

using namespace std;

template <class T>
class substack
{
private:
    T *arr;
    int nextAvailable;
    int size;
public:
    substack(int capacity);
    ~substack();
    void push(T elem);
    T pop();
    T peek();
    bool isfull();
    bool isempty();
};

// Constructor initializing size of substack
template <class T>
substack<T>::substack(int capacity)
{
    nextAvailable = 0;
    size = capacity;
    arr = new T[capacity];
}

// Destructor freeing memory allocated by the stack implemented using array
template <class T>
substack<T>::~substack()
{
    delete[] arr;
    arr = NULL;
}

// Pushing an element on top of a substack of fixed size
template <class T>
void substack<T>::push(T elem)
{
    if (nextAvailable < size)
    {
        arr[nextAvailable] = elem;
        nextAvailable++;
    }
    else
    {
        cout << "Substack is full" << endl;
        return;
    }
}

// Popping the top element from a stack of fixed size
template <class T>
T substack<T>::pop()
{
    nextAvailable--;

    if (nextAvailable >= 0)
    {
        T del = arr[nextAvailable];
        arr[nextAvailable] = NULL;
        return del;
    }
    else
    {
        cout << "Stack is empty" << endl;
        return NULL;
    }
}

// Peeking the top element from a stack of fixed size
template <class T>
T substack<T>::peek()
{
    if (nextAvailable > 0)
    {
        return arr[nextAvailable - 1];
    }
    else
    {
        cout << "Stack is empty" << endl;
        return NULL;
    }
}

// Checking if a substack is full or not
template <class T>
bool substack<T>::isfull()
{
    return (nextAvailable == size);
}

// Checking if a substack is empty or not
template <class T>
bool substack<T>::isempty()
{
    return (nextAvailable == 0);
}

template <class T>
class SetOfStacks
{
private:
    vector<substack<T>*> setofstacks;
    int currStackIndex;
    int size;
public:
    SetOfStacks(int capacity);
    ~SetOfStacks();
    void push(T elem);
    T pop();
    T peek();
};

// Constructor initializing a set of stacks
template <class T>
SetOfStacks<T>::SetOfStacks(int maxStackCapacity)
{
    currStackIndex = 0;
    size = maxStackCapacity;
    //substack<T> *s = new substack<T>(maxStackCapacity);
    setofstacks.push_back(new substack<T>(maxStackCapacity));
}

// Destructor clearing set of stacks vector
template <class T>
SetOfStacks<T>::~SetOfStacks()
{
    setofstacks.clear();
}

// Pushing an element on top of a stack implemented by a set of fixed length substacks
template <class T>
void SetOfStacks<T>::push(T elem)
{
    if (!setofstacks[currStackIndex]->isfull())
    {
        setofstacks[currStackIndex]->push(elem);
    }
    else
    {
        currStackIndex++;
        //substack<T> *s = new substack<T>(size);
        setofstacks.push_back(new substack<T>(size));
        setofstacks[currStackIndex]->push(elem);
    }
}

// Popping an element from top of a stack implemented by a set of fixed length substacks
template <class T>
T SetOfStacks<T>::pop()
{
    if (!setofstacks[currStackIndex]->isempty())
    {
        return setofstacks[currStackIndex]->pop();
    }
    else
    {
        setofstacks.pop_back();
        currStackIndex--;

        if (currStackIndex >= 0)
        {
            return setofstacks[currStackIndex]->pop();
        }
        else
        {
            cout << "Stack is empty" << endl;
            return NULL;
        }
    }
}

// Peeking an element from top of a stack implemented by a set of fixed length substacks
template <class T>
T SetOfStacks<T>::peek()
{
    return setofstacks[currStackIndex].peek();
}

int main()
{
    SetOfStacks<int> *s = new SetOfStacks<int>(5);
    s->push(1);
    s->push(2);
    s->push(3);
    s->push(4);
    s->push(5);

    s->push(6);
    s->push(7);
    s->push(8);

    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;

    s->push(1);
    s->push(2);
    s->push(3);

    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;
    cout << s->pop() << endl;

    system("pause");
}

工作代码

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Press any key to continue . . .

输出

cvs update -r "1.5"

请在添加实际的substack对象时让我知道我在使用push_back时缺少什么，这样它就不会弄乱向量中的先前索引子包。

不确定这是如何成为三人统治的骗局。我错过了三个复制构造函数，赋值运算符之一吗？请帮我理解。