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

typedef struct Node
{
	int data;
	struct Node * pNext;
}NODE,* PNODE;

typedef struct Stack
{
	PNODE pTop;
	PNODE pBottom;
}STACK,* PSTACK;


void init(PSTACK);
void pop(PSTACK ps, int *pval);
bool empty(PSTACK ps);
void traverse(PSTACK ps);
void clear(PSTACK ps);
void push(PSTACK ps,int val);
int main()
{
	STACK s;
	int val;
    init(&s);
	push(&s,1);
	push(&s,2);
	push(&s,3);
	push(&s,4);
	push(&s,5);
	push(&s,6);
	traverse(&s);
	pop(&s,&val);
	printf("出棧的元素值是: %d\n",val);
	traverse(&s);
	clear(&s);
	traverse(&s);
	return 0;
}

void init(PSTACK ps)
{
	ps->pTop = (PNODE)malloc(sizeof(NODE));
	if(NULL == ps->pTop)
	{
		printf("動態記憶體分配失敗！\n");
		exit(-1);
	}
	else
	{
		ps->pBottom = ps->pTop;
		ps->pTop->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;
	ps->pTop = pNew;
}

void pop(PSTACK ps, int *pval)
{
	if(empty(ps))
	{
		return ;//不能寫return true，因為void無返回值
	}
	else
	{
		PNODE r = ps->pTop;
		*pval = r->data;
		ps->pTop = r->pNext;
		free(r);
		r = NULL;
		return;
	}
}

void traverse(PSTACK ps)
{
	PNODE p = ps->pTop;
	while(p != ps->pBottom)
	{
		printf("%d ",p->data);
		p = p->pNext;
	}
	printf("\n");
	return;
}

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->pBottom = ps->pTop;
	}
}