逆波兰式（后缀表达式）的计算

输入 ：后缀表达式（可带浮点数）

输出：double型的计算结果

代码：

#include <stdio.h>

#include <stdlib.h>

#include <malloc.h>

#define ElemType double

#define Stack_Init_Size 100

#define Increase_Size 10

#define MaxBuffer 10

typedef struct sqStack

{

    ElemType *top;

    ElemType *base;

    int initSize;

}sqStack;

typedef struct sqStack *LinkStack;



//初始化

void InitStack( sqStack *s )

{

    s->base = (LinkStack)malloc(Stack_Init_Size * sizeof(ElemType));

    if(!s->base)

    {

        printf("存储空间分配失败······\n");

        return;

    }

    s->top = s->base;

    s->initSize = Stack_Init_Size;

}

//进栈

void Push(sqStack *s,ElemType e)

{

    if(s->top - s->base >= s->initSize - 1)

    {

        s->base = (LinkStack)realloc(s->base,(s->initSize + Increase_Size) * sizeof(ElemType));

        //第一个s->base是增加后的存储空间块的地址，第二个是增加空间之前的存储空间块地址，后面是增加过的存储空间块的大小

        if(!s->base)

        {

            printf("增加存储空间失败······\n");

            return;

        }

        s->initSize = Increase_Size + Stack_Init_Size;

    }

    *(s->top) = e;

    (s->top)++;

}

//出栈

void Pop(sqStack *s,ElemType *e)

{

    if(s->top == s->base)

    {

        printf("栈已空，无法进行出栈操作······\n");

        return;

    }

    s->top--;

    *e = *s->top;

}

//求栈的长度

int StackLen(sqStack s)

{

    return (s.top - s.base);

}



//逆波兰计算器：输入逆波兰式（后缀表达式）输出结果

int main()

{

    int i = 0,j,len;

    double m,n,t;

    char c;

    struct sqStack s;

    char str[MaxBuffer];

    InitStack(&s);

    printf("请输入您要计算的后缀表达式，按Enter键结束（两个不同的字符之间用空格隔开）：\n");

    scanf("%c",&c);

    while(c != '\n')

    {

        while( (c >= '0'&&c <= '9') || c == '.')

        {

            str[i] = c;

            i++;

 //           str[i] = '\0';

            if(i >= 10)

            {

                printf("\n输入的数字过大导致出错！！！\n");

                return -1;

            }

            scanf("%c",&c);

           if( c == ' ')

           {

               t = atof(str);

 //              printf("\nt is %f\n",t);

               Push(&s,t);

               i = 0;

               for(j = 0;j < MaxBuffer;j++)

               {

                   str[j] = '\0';

               }

               break;

           }



        }

        switch( c )

        {

            case '+':

                Pop(&s,&m);

                Pop(&s,&n);

                Push(&s,n+m);

                break;

            case '-':

                Pop(&s,&m);

                Pop(&s,&n);

                Push(&s,n-m);

                break;

            case '*':

                Pop(&s,&m);

                Pop(&s,&n);

                Push(&s,n*m);

                break;

            case '/':

                Pop(&s,&m);

                Pop(&s,&n);

                if( m == 0)

                {

                    printf("\n除数为0，出错！！！\n");

                    return -1;

                }

                else

                {

                    Push(&s,n/m);

                    break;

                }

        }



        scanf("%c",&c);

    }



    Pop(&s,&t);

    printf("\n最终的计算结果为：%f \n",t);

    return 0;

}