数据结构之栈的一些基本操作

#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 pButtom;
}STACK,*PSTACK;

void init(PSTACK); //PSTACK 等价于struct Stack*
void push(PSTACK,int);
void traverse(PSTACK);
bool pop(PSTACK,int*);
bool empty(PSTACK);
void clear(PSTACK); //清空栈

int main(void)
{
    STACK S;//STACK 等价于 struct Stack
    int val;
    init(&S);  //造出一个空栈
    push(&S,1);  //压栈
    push(&S,2);
    push(&S,3);
    push(&S,4);
    push(&S,5);
    push(&S,6);
    push(&S,8);
    traverse(&S);
    if(pop(&S,&val))
    {
        printf("出栈成功!,出栈的元素是:%d ",val);
        printf("出栈后的元素为:");
        traverse(&S); //遍历输出
    }
    else
    {
        printf("出栈失败! ");
    }
   
    clear(&S);
    printf("清空栈后.");
    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! ");
        exit(-1);
    }
    else
    {
       pS->pButtom = pS->pTop;
       pS->pTop->pNext = NULL;//等价于pS->Bottom->pNext = NULL;
    }

}

void push(PSTACK pS,int val)
{
    PNODE pNew = (PNODE)malloc(sizeof(NODE));
    pNew->data = val;
    pNew->pNext = pS->pTop;
    pS->pTop = pNew;
   
    return;
}

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

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;
    }
}

bool empty(PSTACK pS)
{
    if(pS->pTop == pS->pButtom)
    {
        return true;
    }
    else
    {
        return false;
    }
}

void clear(PSTACK pS)
{
    if(empty(pS))
    {
        return ;
    }

    else
    {
        PNODE p = pS->pTop;
        PNODE q = NULL;
        while(p != pS->pButtom)
        {
            q = p->pNext;
            free(p);
            p = q;
        }
        pS->pTop = pS->pButtom;
       
        /*下面的方法也可以实现clear()
        while(pS->pTop != pS->pButtom)
        {
            PNODE p = pS->pTop;
            pS->pTop = pS->pTop->pNext;
            free(p);
            p = NULL;
        } */
    }

}