栈存入数据，就像把东西往箱子里面放一样，先放进去的最后取出来。
如下图所示：

动态栈图.png

一个栈需要两个指针标识栈顶与栈底，栈顶以TOP标识，栈底以BOTTOM来标识。
栈底指针永远指向栈底元素。

代码实现：

typedef struct Node
{
    int nData;
    Node * pNext;
} * PNODE;

typedef struct Stack
{
    PNODE pTop;
    PNODE pBtm;
} *PSTACK;

void initStack(PSTACK pStack);
void push_Stack(PSTACK pStack, int nValue);
bool isEmpty_Stack(const PSTACK pStack);
void show_Stack(const PSTACK pStack);
void pop_Stack(PSTACK pStack);

int main()
{
    Stack oStack;

    initStack(&oStack);
    push_Stack(&oStack, 1);
    push_Stack(&oStack, 2);
    push_Stack(&oStack, 3);
    push_Stack(&oStack, 4);
    push_Stack(&oStack, 5);

    pop_Stack(&oStack);
    pop_Stack(&oStack);
    pop_Stack(&oStack);

    show_Stack(&oStack);
}

void initStack(PSTACK pStack)
{
    
    pStack->pBtm = (PNODE)malloc(sizeof(Node));
    if (nullptr == pStack->pBtm)
    {
        std::cout << "内存申请失败!";
        exit(-1);
    }
    pStack->pBtm->pNext = nullptr;

    pStack->pTop = (PNODE)malloc(sizeof(Node));
    if (nullptr == pStack->pTop)
    {
        std::cout << "内存申请失败!";
        exit(-1);
    }
    pStack->pTop->pNext = pStack->pBtm;
}

void push_Stack(PSTACK pStack, int nValue)
{
    //创建一个新节点
    PNODE pNewNode = (PNODE)malloc(sizeof(Node));
    if (nullptr == pNewNode)
    {
        std::cout << "内存申请失败!";
        exit(-1);
    }

    pNewNode->nData = nValue;

    PNODE pTempNode = pStack->pTop->pNext;
    pNewNode->pNext = pTempNode;
    pStack->pTop->pNext = pNewNode;
}

bool isEmpty_Stack(const PSTACK pStack)
{
    if (pStack->pTop->pNext == pStack->pBtm)
    {
        return true;
    }

    return false;
}

void show_Stack(const PSTACK pStack)
{
    if (isEmpty_Stack(pStack))
    {
        return;
    }

    PNODE pNode = pStack->pTop->pNext;
    while (pNode != pStack->pBtm)
    {
        std::cout << pNode->nData << "\t";
        pNode = pNode->pNext;
    }
}

void pop_Stack(PSTACK pStack)
{
    if (isEmpty_Stack(pStack))
    {
        return;
    }

    PNODE pTempNode = pStack->pTop->pNext;
    pStack->pTop->pNext = pTempNode->pNext;

    std::cout << "删除的元素为：" << pTempNode->nData << "\n";
    free(pTempNode);
}