数据结构之栈

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
//基于链表的动态栈 
typedef struct node{
    int data;
    struct node * pNext;
}NODE,* PNODE;
//设置指向栈顶的指针pTop，以及指向栈底（最下面的一个有效节点的下一个节点）的 指针pBottom 
typedef struct stack{
    PNODE pTop;
    PNODE pBottom;
}STACK,* PSTACK;

//函数声明
void init(PSTACK pS);
void push(PSTACK pS,int val);
bool pop(PSTACK pS,int * pVal);
void clear(PSTACK pS);
void traverse(PSTACK pS);
bool empty(PSTACK pS);
 

int main(void)
{
    STACK s;
    PSTACK pS = &s;
    
    int val;
    int * pVal = &val;
    
    init(pS);
    push(pS,1);
    push(pS,2);
    push(pS,3);
    push(pS,4);
    traverse(pS);
    
    if(pop(pS,pVal))
    {
        printf("出栈成功，出栈元素为：%d\n",*pVal);
    }else{
        printf("出栈失败！！\n");
    }
         
    traverse(pS);
    
    clear(pS);
    traverse(pS);
    return 0;
}
//***************init()初始化栈****************************
void init(PSTACK pS)
{
    pS->pTop = (PNODE)malloc(sizeof(NODE));
    if(pS->pTop==NULL)
    {
        printf("动态内存分配失败！\n");
        exit(-1);
    }else{
        pS->pBottom = pS->pTop;
        pS->pTop->pNext = NULL;
    }
    
}
//***************push()压栈*****************************
void push(PSTACK pS,int val)
{
    PNODE pNew = (PNODE)malloc(sizeof(NODE));
    if(pNew==NULL)
    {
        printf("动态内存分配失败！\n");
        exit(-1);
    }else{
        pNew->data = val;
        pNew->pNext = pS->pTop;
        pS->pTop = pNew;
    }
}
//***************traverse()遍历栈内元素****************************
void traverse(PSTACK pS)
{
    PNODE p = pS->pTop;
    while(p!=pS->pBottom)
    {
        printf("%d  ",p->data);
        p = p->pNext;
    }
    printf("\n");
}
bool pop(PSTACK pS,int * pVal)
{
    if(empty(pS))
    {
        return false;
    }else{
        PNODE q = pS->pTop;
        *pVal = q->data;
        pS->pTop = q->pNext;
        free(q);
        q = NULL;
    }
}
//***************empty()判断栈是否为空**************************** 
bool empty(PSTACK pS)
{
    if(pS->pTop==pS->pBottom)
        return true;
    else
        return false;
}
//***************clear()清空栈内元素，栈为空栈**************************** 
void clear(PSTACK pS)
{
    if(empty(pS))
    {
        printf("栈为空。。。\n");
        return;
    }else{
        PNODE r1 = pS->pTop;
        PNODE r2 = NULL;
        while(r1!=pS->pBottom)
        {
            r2 = r1->pNext;
            free(r1);
            r1 = r2;        
        }
        pS->pTop = pS->pBottom;
        printf("栈已被清空！！\n");
    }
}