C语言实现逆波兰表达式

#include 
#include 
#include 
#define STACK_INIT_SIZE 20
#define STACKINCREMENT 10
#define MAXBUFFER 10

typedef double ElemType;

typedef struct
{
    ElemType *base;
    ElemType *top;
    int stackSize;
}sqStack;

/*
**栈的初始化
*/

void InitStack(sqStack *s)
{
    s->base=(ElemType *)malloc(STACK_INIT_SIZE*sizeof(ElemType));
    if(!s->base)
        exit(0);
    s->top=s->base;
    s->stackSize=STACK_INIT_SIZE;
}

/*
**入栈操作
*/
void Push(sqStack *s,ElemType e)
{
    if(s->top-s->base==s->stackSize)
    {
        s->base=(ElemType *)realloc(s->base,(STACKINCREMENT+s->stackSize)*sizeof(ElemType));
        if(!s->base)
            exit(0);

        s->top=s->base+s->stackSize;
        s->stackSize=s->stackSize+STACKINCREMENT;
    }
    *(s->top)=e;
    s->top++;
}

/*
**出栈操作
*/
void Pop(sqStack *s,ElemType *e)
{
    if(s->top==s->base)
        return;
    *e=*--(s->top);
}

/*
**计算栈的容量
*/
int StackLen(sqStack *s)
{
    return (s->top-s->base);
}
/*
**逆波兰表达式
**正常表达式--->逆波兰表达式
**a+b--->a b +
**a+(b-c)--->a b c - +
**a+(b-c)*d--->a b c - d * +
**a+d*(b-c)--->a d b c - * +
*/
int main()
{
    sqStack s;
    char c;
    double d,e;
    char str[MAXBUFFER];
    int i=0;

    InitStack(&s);
    printf("请输入逆波兰表达式输入待计算数据，数据与运算符之间用空格隔开，以#作为结束标志：\n");

    scanf("%c",&c);
    while(c!='#')
    {
        while(isdigit(c)||c=='.')
        {
            str[i++]=c;
            str[i]='\0';
            if(i>=10)
            {
                printf("error");
                return -1;
            }

            scanf("%c",&c);
            if(c==' ')
            {
                d=atof(str);
                Push(&s,d);
                i=0;
                break;
            }
        }
        switch(c)
        {
        case '+':
            Pop(&s,&e);
            Pop(&s,&d);
            Push(&s,d+e);
            break;
        case '-':
            Pop(&s,&e);
            Pop(&s,&d);
            Push(&s,d-e);
            break;
        case '*':
            Pop(&s,&e);
            Pop(&s,&d);
            Push(&s,d*e);
            break;
        case '/':
            Pop(&s,&e);
            Pop(&s,&d);
            if(e!=0){
                Push(&s,d/e);
            }
            else
            {
                printf("error!");
                return -1;
            }
            break;
        }
        scanf("%c",&c);
    }
    Pop(&s,&d);
    printf("the final result:%f",d);
    return 0;
}