栈的C实现

#include<stdio.h>
#include<stdlib.h>
//定义栈节点结构
typedef struct Node {
     int data;
     struct Node *pNext;    
}NODE,*PNODE;
//定义栈结构
typedef struct Stack{
  PNODE pTop;
  PNODE pBottom;
}STACK,*PSTACK;
void init(PSTACK pStack){
pStack->pTop=(PNODE)malloc(sizeof(NODE));
if(NULL==pStack->pTop){
printf("动态内存分配失败\n");
exit(-1);
}else{
 pStack->pBottom=pStack->pTop;
 pStack->pTop->pNext=NULL;//指针域清空 可以改为pStack->pBottom->pNext=NULL
}

}
//进栈操作
void push(PSTACK pStack,int val){
  PNODE pNew =(PNODE)malloc(sizeof(NODE));
  pNew ->pNext=pStack->pTop;
  pNew ->data=val;
  pStack->pTop=pNew;
  return;
}
void traverse(PSTACK pStack){
 PNODE p=pStack->pTop;
 while(p!=pStack->pBottom){
 printf("%d ",p->data);
 p=p->pNext;
 }
 printf("\n");
 return;

}
//判断是否有为空栈
bool empty(PSTACK pStack){
 if(pStack->pBottom==pStack->pTop){
  return true;
 }else{
  return false;
 }

}
//出栈
bool pop(PSTACK pStack,int *pVal){
 if(empty(pStack)){
 return false;
 }else{
 PNODE r=pStack->pTop;
 pStack->pTop=r->pNext;
 free(r);
 r=NULL;
 return true;
 
 }
}

void clear(PSTACK pStack){
 if(empty(pStack)){
  return ;
 }else{
 PNODE p=pStack->pTop;
 PNODE q=NULL;
 while(p!=pStack->pBottom){
     q=p->pNext;
  free(p);
     p=q;
 }
 pStack->pTop=pStack->pBottom;
 }
}

int main(int argc, char* argv[])
{      int a;
       STACK s;
    init(&s);
    push(&s,1);
       push(&s,2);
    push(&s,3);
    traverse(&s);
    clear(&s);
    traverse(&s);
 scanf("%a",&a);
       return 0;
}