写一个实现浏览器页面前进和后退的

#include <stdio.h>
#include <malloc.h>
#define MaxSize 50
typedef int ElemType;

typedef struct {
    ElemType data[MaxSize];
    int top1, top2;
} DStack;

//初始化共享栈
void InitStack(DStack *&s) {
    s = (DStack *)malloc(sizeof(DStack));
    s->top1 = -1;
    s->top2 = MaxSize;
}

//销毁共享栈
void DestroyDStack(DStack *&s) {
    free(s);
}

//判断栈是否为空
bool StackEmpty(DStack *s, int which) { //which指示需判断哪个栈是否为空
    if (which == 1)
        return (s->top1 == -1);
    if (which == 2)
        return (s->top2 == MaxSize);
}

//判断栈是否已满
bool StackFull(DStack *s) {
    return (s->top1 == s-> top2 - 1);
}

//进栈
bool Push(DStack *&s, ElemType &e, int which) { //which指示取哪个栈的栈顶元素赋给e
    if (s->top1 == s->top2 - 1)
        return false;
    if (which == 1)
        s->top1++;
    s->data[s->top1] = e;
    if (which == 2)
        s->top2--;
    s->data[s->top2] = e;
}

//出栈
bool Pop(DStack *&s, ElemType &e, int which) { //which从哪个栈弹出栈顶元素赋给e
    if (which == 1)
        if (s->top1 == -1)
            return false;
    e = s->data[s->top1];
    s->top1--;
    return true;
    if (which == 2)
        if (s->top2 == MaxSize)
            return false;
    e = s->data[s->top2];
    s->top2++;
    return true;
}

//取栈顶元素
bool GetTop(DStack *s, ElemType &e, int which) { //which指示取哪个栈的栈顶元素赋给e
    if (which == 1)
        if (s->top1 == -1)
            return false;
    e = s->data[s->top1];
    return true;
    if (which == 2)
        if (s->top2 == MaxSize)
            return false;
    e = s->data[s->top2];
    return true;
}

//利用共享栈实现浏览器的前进与后退
//浏览一个新页面
bool Vist(DStack *&s, ElemType e) { //若栈已满，返回 false；否则返回 true
    if (StackFull(s))
        return false;
    else {
        Push(s, e, 1);
        return true;
    }
}

//后退浏览前一页面
bool Backward(DStack *&s, ElemType &e) { //若无法继续后退，返回 false；否则，将前一页面赋给 e，并且返回 true
    if (StackFull(s) || s->top1 <= 0)
        return false;
    else {
        Pop(s, e, 1);
        Push(s, e, 2);
        e = s->data[s->top1];
        return true;
    }
}

//前进浏览后一页面
bool Forward(DStack *&s, ElemType &e) { //若无法继续前进，返回 false；否则，将后一页面赋给 e，并且返回 true
    if (StackEmpty(s, 1) || StackEmpty(s, 2))
        return false;
    else {
        Pop(s, e, 2);
        Push(s, e, 1);
        e = s->data[s->top2];
        return true;
    }
}

int main() {
    DStack s;
    int i;
    char e, a, b, c;
    char num[3];
    InitStack(s);
    for (i = 0; i < 3; i++)
        scanf("%c", num[i]);
    for (i = 0; i < 3; i++)
        Vist(s, num[i]);
    Backward(s, c);
    printf("%d", e);
    Backward(s, b);
    printf("%d", e);
    Backward(s, a);
    printf("%d", e);
    return 0;
}

主函数只是编写了一部分，试着运行了一下，发现出问题了，然后找不到问题