c语言之动态栈的功能实现

#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;

//在函数声明时可以只写变量类型，不写形参的变量名
void initStack(PSTACK pS);//初始化
bool push(int val,PSTACK pS);//压栈
bool pop(PSTACK pS,int * val);//出栈并返回元素
bool isEmpty(PSTACK);
void travelStack(PSTACK);
void clear(PSTACK pS);

int main()
{
bool p,q,r,s;
int val;
PSTACK pS = (PSTACK)malloc(sizeof(STACK));
//PSTACK pS;之前写成了这样没有分配内存导致程序退出，还有一种解决办法：STACK pS；initStack(&pS)

r = isEmpty(pS);
if(r)
printf("该栈为空栈\n");
else
printf("该栈不为空\n");

initStack(pS);

p = push(1,pS);
if(p)
{
printf("入栈成功\n");
}
else
{
printf("入栈失败\n");
}

r = isEmpty(pS);
if(r)
printf("该栈为空栈\n");
else
printf("该栈不为空\n");

/*	q = pop(pS,&val);
if(q)
printf("出栈元素为:%d\n",val);

s = isEmpty(pS);
if(s)
printf("该栈为空栈\n");
else
printf("该栈不为空\n");
*/
travelStack(pS);

clear(pS);

r = isEmpty(pS);
if(r)
printf("该栈为空栈\n");
else
printf("该栈不为空\n");
return 0;
}

void initStack(PSTACK pS)
{
pS->pTop = (PNODE)malloc(sizeof(NODE));
if(pS->pTop == NULL)
{
printf("动态内存分配失败，程序退出\n");
exit(-1);
}
pS->pBottom = pS->pTop;
pS->pTop->pNext = NULL;
//是next不是pS->pTop = NULL;这会导致pS永远不为空！！

}

bool push(int val,PSTACK pS)
{
PNODE pNew = (PNODE)malloc(sizeof(NODE));
if(pNew == NULL)
{
return false;
}
else
{
pNew->data = val;
pNew->pNext = pS->pTop;
pS->pTop = pNew;
return true;
}
}

//bool pop(PSTACK pS,int val)切记不要把*丢掉，因为只把变量名传进去是不会改变元素的值的，只有把地址传进去才可以！！！
bool pop(PSTACK pS,int * val)
{
if(isEmpty(pS))
{
return false;
}
else
{
PNODE p = pS->pTop;
*val = p->data;
pS->pTop = p->pNext;
free(p);
p = NULL;
return true;
}
}

bool isEmpty(PSTACK pS)
{
PNODE p = pS->pTop;
if(p != pS->pBottom)
return false;
return true;
}

void travelStack(PSTACK pS)
{
if(isEmpty(pS))
{
return;
}
else
{
PNODE p = pS->pTop;
while(p != pS->pBottom)
{
printf("%d\t",p->data);
p = p->pNext;
}
printf("\n");
}
}

void clear(PSTACK pS)
{
if(isEmpty(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;//不写这句话会导致pS一直不为空！
}
}