# include <stdio.h>
# include <malloc.h>
# include <stdlib.h>

typedef struct Node
{
    int data;                //数据
    struct Node * pNext;    //指向下一个结点
}NODE, * PNODE;

typedef struct Stack
{
    PNODE pTop;            //栈顶指针
    PNODE pBottom;        //栈底指针
}STACK, * PSTACK;  //PSTACK 等价于 struct STACK *

void init(PSTACK);        //初始化创造空结点
void push(PSTACK, int );//压栈
void traverse(PSTACK);//遍历
bool pop(PSTACK, int *);//出栈
void clear(PSTACK pS);//清栈

void init(PSTACK pS)
{
    pS->pTop = (PNODE)malloc(sizeof(NODE));//创造空结点给栈地指针；
    if (NULL == pS->pTop)
    {
        printf("动态内存分配失败!\n");
        exit(-1);
    }
    else
    {
        pS->pBottom = pS->pTop;//栈顶指针=栈底指针
        pS->pTop->pNext = NULL; //pS->Bottom->pNext = NULL;
    }
}

bool empty(PSTACK pS)
{
    if (pS->pTop == pS->pBottom)
        return true;
    else
        return false;
}

void push(PSTACK pS, int val)
{
    PNODE pNew = (PNODE)malloc(sizeof(NODE));
    
    pNew->data = val;
    pNew->pNext = pS->pTop; //新结点指向原栈顶指针指向的结点
    pS->pTop = pNew;        //栈顶指针为指向新结点

    return;
}

//把pS所指向的栈出栈一次，并把出栈的元素存入pVal形参所指向的变量中，如果出栈失败，返回false,否则返回true
bool pop(PSTACK pS, int * pVal)
{
    if ( empty(pS) ) //pS本身存放的就是S的地址
    {
        return false;
    }
    else
    {
        PNODE r = pS->pTop;
        *pVal = r->data;
        pS->pTop = r->pNext;
        free(r);
        r = NULL;

        return true;
    }
}

void traverse(PSTACK pS)
{
    PNODE p = pS->pTop;

    while (p != pS->pBottom)
    {
        printf("%d  ", p->data);
        p = p->pNext;
    }
    printf("\n");

    return;
}

//clear清空
void clear(PSTACK pS)
{
    if (empty(pS))
    {
        return;
    }
    else
    {
        PNODE p = pS->pTop;
        PNODE q = NULL;

        while (p != pS->pBottom)
        {
            q = p->pNext;
            free(p);
            p = q;
        }
        pS->pTop = pS->pBottom;
    }
}