6-11 在一个数组中实现两个堆栈 (20 分)
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

//两栈共享空间
//S->Top1 + 1 == S->Top2栈满
Stack CreateStack( int MaxSize )
{struct SNode *S=NULL;S=(struct SNode *)malloc(sizeof(struct SNode));//为S这个节点开辟空间S->Data=(int *)malloc(MaxSize*sizeof(int));//为S中的数据开辟MaxSize的空间S->Top1=-1;//栈1空，栈顶指针S->Top2=MaxSize;//栈2空，栈顶指针S->MaxSize=MaxSize;return S;
}
bool Push( Stack S, ElementType X, int Tag )//Tag是堆栈编号
{if(S->Top2 - S->Top1==1){printf("Stack Full\n");return false;}else{if(Tag==1) S->Data[++(S->Top1)]=X;else if(Tag==2) S->Data[--(S->Top2)]=X;return true;}
}
ElementType Pop( Stack S, int Tag )
{if(Tag==1){if(S->Top1==-1){printf("Stack %d Empty\n",Tag);return ERROR;}else{return S->Data[(S->Top1)--];}}else if(Tag==2){if(S->Top2==S->MaxSize){printf("Stack %d Empty\n",Tag);return ERROR;}else{return S->Data[(S->Top2)++];}}
}