数据结构-栈

#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 pBottom;
}STACK,*PSTACK;

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

int main(void)
{
    int val;
    STACK S;
    init(&S);
    push(&S,1);
    push(&S,2);
    pop(&S,&val);
    traverse(&S);
    clear(&S);
    return 0;
}

void init(PSTACK pS)
{
    pS->pTop = (PNODE)malloc(sizeof(NODE));
    if (NULL == pS->pTop)
    {
        printf("malloc fail!");
        exit(-1);
    }
    else
    {
        pS->pBottom = pS->pTop;
        pS->pTop->pNext = NULL;
    }
}


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

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

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