两栈共享空间

#define MAXSIZE 100

struct doublestack
{
    int number[MAXSIZE];
    int top1=-1;
    int top2=MAXSIZE;
};


void Push(doublestack *s, int e, int n)
{
    //栈满
    if (s->top1 + 1 == s->top2)
        exit(1);
    if (n == 1)
    {
        s->top1++;
        s->number[s->top1]=e;
    }
    else if (n == 2)
    {
        s->top2--;
        s->number[s->top2] = e;
    }
}


int Pop(doublestack *s, int n)
{
    int t;
    if (n == 1)
    {
        if (s->top1 == -1)
            return -1;
        t = s->number[s->top1--];
    }
    else if (n == 2)
    {
        if (s->top2 == MAXSIZE)
            return -1;
        t = s->number[s->top2++];
    }
    return t;
}