PTA 6-7 在一个数组中实现两个堆栈C语言详解

6-7 在一个数组中实现两个堆栈 (20分)
题目出处
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：
裁判测试程序样例：
本blog已经把Operation GetOp(); /* details omitted */补写，且在主程序中注释掉void PrintStack( Stack S, int Tag ); /* details omitted */

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。

#include <stdio.h>
#include <stdlib.h>
#include <string.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;//Data[MaxSize]
    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 */

Operation GetOp(){
    char a[5];
    scanf("%s",a);
    if(strcmp(a,"Push")==0) return push;
    if(strcmp(a,"Pop")==0) return pop;
    if(strcmp(a,"End")==0) return end;
}

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;
}

题解代码

/* 你的代码将被嵌在这里 */
Stack CreateStack( int MaxSize )
{
    Stack s;
    s=(Stack)malloc(sizeof(Stack));
    s->Data=(ElementType*)malloc(sizeof(ElementType)*MaxSize);
    s->MaxSize=MaxSize;
    s->Top1=-1;
    s->Top2=MaxSize;
    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;
        return true;
    }
    else
    {
        S->Top2--;
        S->Data[S->Top2]=X;
        return true;
    }
    
}
ElementType Pop( Stack S, int Tag )
{
    if(Tag == 1 && (S->Top1)==-1)
    {
        printf("Stack 1 Empty\n");
        return ERROR;
    }
    else if(Tag == 2 && (S->Top2) == S->MaxSize)
    {
        printf("Stack 2 Empty\n");
        return ERROR;
    }
    else 
    {
        
        if(Tag==1)
             return S->Data[(S->Top1)--];   
             /*{
             int top;
             top=S->Data[S->Top1];
            S->Top1--;
            return top;
            }*/
       
        else if(Tag==2)
             return S->Data[(S->Top2)++];     
    }
}