顺序栈的建立及操作

问题:建立顺序栈还是比较简单的。主要是一开始在入栈操作中每次调用初始化栈函数，结构出错。

代码：

#include <iostream>
#include <cstdlib>
using namespace std;
#define MAXSIZE 20
typedef struct SeqStack
{
    int stack [MAXSIZE];
    int top;
}*stackNode;
 
void initStack(stackNode &stack)
{
    stack=(stackNode)malloc(sizeof(struct SeqStack));
    if(!stack)
    {
        cout<<"allocate fail"<<endl;
        exit(EXIT_FAILURE);
    }
    else
    {
        stack->top=-1;
    }
}
 
void pushStack(stackNode stack,int elem)
{
     if(stack->top==MAXSIZE)
     {
         cout<<"stack is full"<<endl;
         exit(0);
     }
     else
     {
         stack->stack[++(stack->top)]=elem;
     }
}
 
int  popStack(stackNode stack)
{
    int elem;
    if(stack->top==-1)
    {
        cout<<"栈已空"<<endl;
        return -1;
    }
    elem=stack->stack[stack->top];
    --stack->top;
 
    return elem;
}
 
int topStack(stackNode stack)
{
    int top;
    if(stack->top==-1)
    {
        cout<<"栈已空"<<endl;
        return -1;
    }
    top=stack->stack[stack->top];
 
    return top;
}
 
void showStack(stackNode stack)
{
    if(stack->top==-1)
    {
        cout<<"栈已空"<<endl;
        exit(-1);
    }
    while(stack->top!=-1)
    {
        cout<<stack->stack[stack->top]<<"--";
        --stack->top;
    }
    cout<<endl;
}
 
int main()
{
    stackNode stack=NULL;
    int top;
    int arr[]={1,3,5,6,7,2,9,8};
    initStack(stack);
    cout<<"入栈:"<<endl;
    for(int i=0;i<8;i++)
    {
        pushStack(stack,arr[i]);
    }
 
    top=topStack(stack);
    cout<<"top="<<top<<endl;
 
    cout<<"出栈元素为"<<popStack(stack)<<endl;
    cout<<"出栈元素为"<<popStack(stack)<<endl;
 
    cout<<"入栈:"<<endl;
    pushStack(stack,16);
    pushStack(stack,19);
 
    top=topStack(stack);
    cout<<"top="<<top<<endl;
    cout<<"遍历栈中的元素:";
    showStack(stack);
    return 0;
}