棧的基本操作

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

typedef struct Node{
    int data;
    struct Node *pNext;
}NODE,*PNODE;

typedef struct Stack{
    PNODE pTop;//頂部
    PNODE pBottom;//底部
}STACK,*PSTACK;

void initStack(PSTACK);
void pushStack(PSTACK,int val);
void traverse(PSTACK);
bool pop(PSTACK,int *);
bool empty(PSTACK pS);

int main()
{
    STACK S;//一開始什麼都沒有，是垃圾值
    int val;
    initStack(&S);

    pushStack(&S,1);
    pushStack(&S,2);
    pushStack(&S,3);
    pushStack(&S,4);
    pushStack(&S,5);
    pushStack(&S,6);

    if(pop(&S,&val)){
       printf("出棧成功，出棧的元素是%d\n",val);
    }else{
        printf("出棧失敗\n");
    }
    traverse(&S);
    clear(&S);
    traverse(&S);
    return 0;
}

void initStack(PSTACK pS){
    pS->pTop = (PNODE)malloc(sizeof(NODE));
    if(pS->pTop==NULL){
       printf("動態內存分配失敗！\n");
       exit(-1);
    }else{
       pS->pBottom=pS->pTop;
    }
}

void pushStack(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->pBottom){
        printf("%d \n",p->data);
        p=p->pNext;
    }
    printf("\n");
    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->pBottom){
        return true;
    }else{
        return false;
    }

}

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=NULL;
             p = q;
        }
        pS->pTop = pS->pBottom;
    }
}