用两个栈模拟无限长队列

#include <stdio.h>
#include <stdlib.h>
#define STACK_INIT_SIZE 3//定义栈初始空间的容量
#define STACKINCREMENT 3//存储空间的分配增量
typedef char elementtype;
//栈1作入栈用,栈2作出栈用
typedef struct sqstack{
    elementtype *top;//栈顶指针
    elementtype *base;//栈底指针
    int stacksize;//当前已分配的空间,以栈元素的个数为单位
}sqstack;
sqstack *s1 = (sqstack*)malloc(sizeof(sqstack));
sqstack *s2 = (sqstack*)malloc(sizeof(sqstack));
int inistack()
{
    s1->base = (elementtype*)malloc(sizeof(elementtype)*STACK_INIT_SIZE);//access violation
    s2->base = (elementtype*)malloc(sizeof(elementtype)*STACK_INIT_SIZE);
    if(!s1->base && !s2->base)
        return 0;
     s1->top = s1->base;//栈空时,栈顶指针和栈底指针位置相同
    s2->top = s2->base;
    s1->stacksize = s2->stacksize = STACK_INIT_SIZE;
    return 1;
}
int enstack(char t,int c)
{
    if(c == 1)
    {
        if(s1->top - s1->base == s1->stacksize)//栈1满
        {
            s1->base = (elementtype*)realloc(s1->base,sizeof(elementtype)*(s1->stacksize+STACKINCREMENT));//追加存储空间
            if(!s1->base)//空间开辟失败
                return 0;
            s1->stacksize += STACKINCREMENT;//修改栈容量
        }
        *(s1->top)++ = t;
        return 1;
    }
    else{
        if(s2->top - s2->base == s2->stacksize)//栈2满
        {
            s2->base = (elementtype*)realloc(s2->base,sizeof(elementtype)*(s2->stacksize+STACKINCREMENT));//追加存储空间
            if(!s2->base)//空间开辟失败
                return 0;
            s2->top = s2->base + s2->stacksize;//修改栈顶指针的新值
            s2->stacksize += STACKINCREMENT;//修改栈容量
        }
        *(s2->top)++ = t;
        return 1;
    }
}
int popstack(char &t)
{
    if(s2->top == s2->base)//栈2空
    {
        if(s1->top == s1->base)//如果栈1也空,则队列为空
            return 0;
        else{//栈1的所有元素出栈,入栈2
            while(s1->top != s1->base)
            {
                enstack(*(--s1->top),2);//入栈2
            }
        }
    }
    t = *(--s2->top);
    return 1;
}
void QueueMenu()
{
    printf("\t\t\t~~~两个栈模拟无限长队列~~~\n");
    printf("\t\t\t\t1.元素入队\n");
    printf("\t\t\t\t2.元素出队\n");
    printf("\t\t\t\t3.显示队列\n");
    printf("\t\t\t\t4.清空队列\n");
}
int enqueue(char t)
{
    return enstack(t,1);
}
int dequeue(char &t)
{
    return popstack(t);
}
int showqueue()
{
    if(s2->top == s2->base && s1->top == s1->base)
        return 0;
    else{
        printf("队列元素为:");
        elementtype *s = s2->top;
        while(s != s2->base)
            printf("%c ",*(--s));
        //此处依然是栈的操作
        s = s1->base;
        while(s1->top != s)
            printf("%c ",*s++);
        printf("\n");
        return 1;
    }
}
int delqueue()
{
    free(s1->base);
    free(s2->base);
    return inistack();
}
int main()
{
    int a;
    inistack();
    while(1)
    {
        QueueMenu();
        printf("请输入你的选择:");
        scanf("%d",&a);
        while(a < 1 || a > 4)
        {
            fflush(stdin);//清除缓存
            system("pause");
            system("cls");
            QueueMenu();
            printf("请重新输入你的选择:");
            scanf("%d",&a);
        }
        //inistack();
        char t;
        switch(a)
        {
        case 1:
            fflush(stdin);//
            printf("请输入要入队的元素:");
            scanf("%c",&t);
            if(enqueue(t))
                printf("元素入队成功!\n");
            else
                printf("队满,元素入队失败!\n");
            break;
        case 2:
            if(dequeue(t))
                printf("出队元素为:%c\n",t);
            else
                printf("队空!出队失败!\n");
            break;
        case 3:
            if(!showqueue())
                printf("队列为空!\n");
            break;
        default:
            if(delqueue())
                printf("队列清空\n");
            else
                printf("重新创建失败,队列未被清空\n");
        }
        fflush(stdin);
        system("pause");
        system("cls");
    }
    return 0;
}