C语言对栈的实现基本操作

#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
#include <stdbool.h>
 
typedef struct Node
{
 int data;
 struct Node * pNext;
}NODE, * PNODE;
 
typedef struct Stack
{
 PNODE pTop;
 PNODE pBottom;
}STACK, * PSTACK; //PSTACK等价于struct STACK *
 
void init(PSTACK); //初始化栈
void push(PSTACK, int ); //压栈
void traverse(PSTACK); //遍历
bool pop(PSTACK pS,int * pVal); //出栈
void clear(PSTACK pS); //清空栈
 
int main(void)
{
 STACK S; //STACK等价于struct Stack
 int val;
 init(&S); //造出空栈
 
 push(&S, 1); //压栈
 push(&S, 2);
 push(&S, 3);
 push(&S, 4);
 push(&S, 5);
 push(&S, 6);
 
 traverse(&S); //遍历输出
/*
 if(pop(&S,&val))
 {
 printf("出栈成功，出栈的元素是%d\n", val);
 }
 else
 {
 printf("出栈失败！\n");
 }
*/ 
 clear(&S);
 traverse(&S);
 
 return 0;
}
 
void init(PSTACK pS)
{
 pS->pTop = (PNODE)malloc(sizeof(NODE));
 if(NULL == pS->pTop)
 {
 printf("动态内存分配失败\n");
 exit(-1);
 }
 else
 {
 pS->pBottom = pS->pTop;
 pS->pTop->pNext = NULL;
 }
}
 
void push(PSTACK pS, int val)
{
 PNODE pNew = (PNODE)malloc(sizeof(NODE)); //创建新的节点
 pNew->data = val; //将val的值赋给新节点的数据域
 pNew->pNext = pS->pTop; //将新节点的指针域指向下一个节点.pS->Top不能改写成pS->Bottom
 pS->pTop = pNew; //pTop指向新节点
 return;
}
 
void traverse(PSTACK pS)
{
 PNODE p = pS->pTop;
 while(p != pS->pBottom)
 {
 printf("%d ", p->data);
 p = p->pNext;
 }
 printf("\n");
 return;
}
 
bool empty(PSTACK pS)
{
 if(pS->pTop == pS->pBottom)
 {
 return true;
 }
 else
 {
 return false;
 }
}
 
bool pop(PSTACK pS,int * pVal)
{
 if(empty(pS))
 {
 return false;
 }
 else
 {
 PNODE r = pS->pTop;
 *pVal = r->data;
 pS->pTop = r->pNext;
 free(r);
 r = NULL;
 return true;
 }
}
 
//清空栈
void clear(PSTACK pS)
{
 if(empty(pS)) //如果
 {
 return;
 }
 else
 {
 PNODE p = pS->pTop; //定义元素p指向栈顶元素
 PNODE q = NULL； //定义元素q，初始值为空
  
 while(p !=pS->pBottom) //如果栈不为空
 {
  q = p->pNext; //q指向p的下一个元素
  free(p);  //释放p所指向的栈顶元素
  p = q;  //将q所指向的元素赋给p
 }
 pS->pTop = pS->pBottom; 
 }
}