4-7 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 1e8typedef 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：

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

输出样例：

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

点击访问 PAT-测验

Stack CreateStack( int MaxSize ){    Stack S = (Stack)malloc(sizeof(struct SNode));    S->MaxSize = MaxSize;    S->Data = (ElementType *)malloc(sizeof(ElementType)*MaxSize);    S->Top2 = MaxSize;    S->Top1 = -1;    return S;}bool Push(Stack S, ElementType X, int Tag){    if(S->Top1+1 == S->Top2){        printf("Stack Full\n");        return false;    }else{        if(Tag == 1){            S->Top1++;            S->Data[S->Top1] = X;        }else{            S->Top2--;            S->Data[S->Top2] = X;        }    }    return true;}ElementType Pop(Stack S, int Tag){    int X;    if(Tag == 1){        if(S->Top1 == -1){            printf("Stack 1 Empty\n");            return ERROR;        }else{            X = S->Data[S->Top1];            S->Top1--;            return X;        }    }else if(Tag == 2){        if(S->Top2 == S->MaxSize){            printf("Stack 2 Empty\n");            return ERROR;        }else{            X = S->Data[S->Top2];            S->Top2++;            return X;        }    }}