栈—代码

#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>

//局部变量在栈里面分配。静态分配都在栈里面分配，动态都在堆里面分派的。

typedef struct Node
{
    int data;
    struct Node *pNext;
}NODE, * PNODE;                //NODE等价于struct Node。PNODE等价于struct Node*

typedef struct Stack
{
    PNODE pTop;
    PNODE pButtom;
}STACK, * PSTACK;//

void init(PSTACK);
void push(PSTACK, int);
void traverse(PSTACK);
bool pop(PSTACK, int *);
void clear(PSTACK);


int main(void)
{
    int val;
    STACK S;
    init(&S);
    push(&S, 1);
    push(&S, 2);
    push(&S, 3);
    push(&S, 4);
    push(&S, 5);
    push(&S, 6);
    push(&S, 7);
    push(&S, 8);
    traverse(&S);
    clear(&S);
    traverse(&S);
    if(pop(&S, &val))
    {
        printf("出栈成功，出栈的元素是%d\n",val);
    }
    else
    {
        printf("出栈失败");
    }
    return 0;
}

void init(PSTACK pS)
{
    pS->pTop = (PNODE)malloc(sizeof(NODE));
    if (NULL == pS->pTop)
    {
        printf("动态分配失败！\n");
        exit(-1);
    }
    else
    {
        pS->pButtom = pS->pTop;
        pS->pButtom->pNext = NULL;//pS->pTop->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("\n");
    return;
}

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


//把pS所指向的栈出栈一次，并把出栈的元素存入pVal形参所指向的变量中。如果出栈失败返回false。
bool pop(PSTACK pS, int *pVal)
{
    if(empty(pS))   //pS本身存放的就是S的地址
    {
        return false;
    }
    else
    {
        PNODE q = pS->pTop;    
        *pVal = q->data;
        pS->pTop = q->pNext;
        free(q);
        q = NULL;
        return true;
    }
}

//清空数据
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;
    }
}