2020.10.8问题.

本题要求在一个数组中实现两个堆栈。

函数接口定义：

Stack CreateStack( int MaxSize );
bool Push( Stack S, ElementType X, int Tag );
ElementType Pop( Stack S, int Tag );

其中Tag是堆栈编号，取1或2；MaxSize堆栈数组的规模；Stack结构定义如下：

typedef int Position;
struct SNode {
    ElementType *Data;
    Position Top1, Top2;
    int MaxSize;
};
typedef struct SNode *Stack;

注意：如果堆栈已满，Push函数必须输出“Stack Full”并且返回false；如果某堆栈是空的，则Pop函数必须输出“Stack Tag Empty”（其中Tag是该堆栈的编号），并且返回ERROR。

裁判测试程序样例：

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

#define ERROR 1e8
typedef int ElementType;
typedef enum { push, pop, end } Operation;
typedef enum { false, true } bool;
typedef int Position;
struct SNode {
    ElementType *Data;
    Position Top1, Top2;
    int MaxSize;
};
typedef struct SNode *Stack;

Stack CreateStack( int MaxSize );
bool Push( Stack S, ElementType X, int Tag );
ElementType Pop( Stack S, int Tag );

Operation GetOp();  /* details omitted */
void PrintStack( Stack S, int Tag ); /* details omitted */

int main()
{
    int N, Tag, X;
    Stack S;
    int done = 0;

    scanf("%d", &N);
    S = CreateStack(N);
    while ( !done ) {
        switch( GetOp() ) {
        case push: 
            scanf("%d %d", &Tag, &X);
            if (!Push(S, X, Tag)) printf("Stack %d is Full!\n", Tag);
            break;
        case pop:
            scanf("%d", &Tag);
            X = Pop(S, Tag);
            if ( X==ERROR ) printf("Stack %d is Empty!\n", Tag);
            break;
        case end:
            PrintStack(S, 1);
            PrintStack(S, 2);
            done = 1;
            break;
        }
    }
    return 0;
}

/* 你的代码将被嵌在这里 */

输入样例：

5
Push 1 1
Pop 2
Push 2 11
Push 1 2
Push 2 12
Pop 1
Push 2 13
Push 2 14
Push 1 3
Pop 2
End

输出样例：

Stack 2 Empty
Stack 2 is Empty!
Stack Full
Stack 1 is Full!
Pop from Stack 1: 1
Pop from Stack 2: 13 12 11

存在的问题：

以下为自己写的代码，理论上逻辑并没有问题，但是运行一直超时。

Stack CreateStack(int MaxSize)
{
    Stack S = (Stack)malloc(sizeof(struct SNode));
    S->Data = (int*)malloc(MaxSize * sizeof(int));
    S->Top1 = 0;
    S->Top2 = MaxSize-1;
    S->MaxSize = MaxSize;
    return S;
}

bool Push(Stack S, ElementType X, int Tag)
{
    if (S->Top1 > S->Top2)
    {
        printf("Stack Full\n");
        return false;
    }


    if (Tag == 1)
    {
        S->Data[S->Top1++] = X;
    }
    else
    {
        S->Data[S->Top2--] = X;
    }
    return true;
}



ElementType Pop(Stack S, int Tag)
{
    if (Tag == 1)
    {
        if (S->Top1 == 0)
        {
            printf("Stack %d Empty\n", Tag);
            return ERROR;
        }
        return S->Data[--S->Top1];
    }
    
    if (S->Top2 == S->MaxSize-1)
    {
        printf("Stack %d Empty\n", Tag);
        return ERROR;
    }
    return S->Data[++S->Top2];
}

而其他大佬的代码

Stack CreateStack(int MaxSize)//双栈结构即为两个栈共享一块空间
{
    Stack stack = (struct SNode *)malloc(sizeof(struct SNode));//先为栈分配一个空间
    stack->Data = (int *)malloc(sizeof(ElementType)* MaxSize);//为栈分配一个Macsize大小的数组空间存放值
    stack->Top1 = -1;
    stack->Top2 = MaxSize;
    stack->MaxSize = MaxSize;
    return stack;
}

bool Push(Stack S, ElementType X, int Tag)//入栈操作
{
    if (!S)//这个栈空间不存在，分配失败的时候
        return false;
    if (S->Top1+1==S->Top2)//栈满的情况
    {
        printf("Stack Full\n");
        return false;
    }

    if (Tag == 1)
       
        S->Data[++S->Top1] = X;
     else 
         S->Data[--S->Top2] = X;
     return true;
}

ElementType Pop(Stack S, int Tag)
{
    if (!S)
        return ERROR;
    if (Tag == 1)
    {
        if (S->Top1 == -1)
        {
            printf("Stack %d Empty\n",Tag);
            return ERROR;
        }
        return S->Data[S->Top1--];
    }
    
    if (S->Top2 == S->MaxSize)
    {
        printf("Stack %d Empty\n", Tag);
        return ERROR;
    }
    return S->Data[S->Top2++];
    
    
}