程序代码：

#include<stdio.h>
#include<stdlib.h>
#define stackmaxsize 100
#define stackincert 10

typedef struct
{
    float *top;
    float *base;    
    int stacksize;
}NumStack;

typedef struct
{
    char *top;
    char *base;
    int stacksize;
}CharStack;

int stackinit_num(NumStack *s) 
{
    s->base = (float*)malloc(stackmaxsize*sizeof(float));
    if(s->base == NULL) 
        exit(1);
    s->top = s->base;    
    s->stacksize = stackmaxsize;
    return 0;
}

int stackinit_flag(CharStack *p)
{
    p->base=(char*)malloc(stackmaxsize*sizeof(char)); 
    if(p->base==NULL) exit(1);
    p->top=p->base;    
    p->stacksize=stackmaxsize;
    return 0;
}
int push_num(NumStack *s,float x)
{
     if(s->top-s->base>=s->stacksize)
     {
          s->base=(float*)realloc(s->base,(s->stacksize+stackincert)*sizeof(float));    
          if(s->base==NULL) exit(1);
          s->top=s->base+s->stacksize;
          s->stacksize+=stackincert;    
     }
     *(s->top++)=x;
     return 0;
}

int push_flag(CharStack *w,char x)
{
     if(w->top-w->base>=w->stacksize)
     {
          w->base=(char*)realloc(w->base,(w->stacksize+stackincert)*sizeof(char));    
          if(w->base==NULL) exit(1);
          w->top=w->base+w->stacksize;
          w->stacksize+=stackincert;    
     }
     *(w->top++)=x;
     return 0;
}

int pop_num(NumStack *s_num,float *x)
{
    if(s_num->top==s_num->base) 
        exit(1);
    *x=*(--s_num->top);    
        return 0;
}

int pop_flag(CharStack *s_flag,char *x)
{
    if(s_flag->top==s_flag->base)
        exit(1);
    *x=*(--s_flag->top);    
        return 0;
}
    
int gettop_flag(CharStack s,char *x)
{
    if(s.top==s.base) 
        exit(1);
    *x=*(--s.top);    
    return 0;
}

int compare(char *p1,char *p2)
{
    if(*p1=='+'||*p1=='-')
       {
           if(*p2=='+'||*p2=='-'||*p2==')'||*p2=='#')
               return 1;
           else 
               return -1;
        }    
    else if(*p1=='*'||*p1=='/')
       {
           if(*p2=='(') 
               return -1;
           else 
               return 1;
       }
    else  if(*p1=='(') 
       {
            if(*p2==')') 
                return 0;
            else if(*p2=='#') 
            {
                printf("表达式错误");
                exit(1);
            }
               else 
                   return -1;
       }
      else if(*p1==')')
        {
         if(*p2=='(') 
         {
             printf("表达式错误");
             exit(1);
         }
         else 
             return 1;    
        }
      else  if(*p1=='#') 
             {
                  if(*p2==')') {printf("表达式错误");exit(1);}
                  else if(*p2=='=') return 0;    
                     else return -1;
             }
             else 
             {
                 printf("表达式错误");
                 exit(1);
             }
}

int function(float a,char ch,float b,float *y)
{
    if(ch == '+') //判断==
    *y=a+b;
    else if(ch == '-') *y=a-b;
    else if(ch == '*') *y=a*b;
    else if(ch == '/') *y=a/b;
    else 
    {
        printf("error");
        exit(1);
    }
    return 0;    
}



int main()
{
    NumStack s_num;
    CharStack s_flag;
    char ch1,ch2;
    float a,b,c;
    char z[20];
    int i;
    stackinit_flag(&s_flag);
    push_flag(&s_flag,'#');
    stackinit_num(&s_num);
    printf("请输入表达式，例如：(3+4)*5#\n");
    ch1=getchar();
    gettop_flag(s_flag, &ch2);
    while(ch1!='#'||ch2!='#')
    {
       if(ch1!='+'&&ch1!='-'&&ch1!='*'&&ch1!='/' && ch1!='(' &&ch1!=')' &&ch1!='#') //加了ch1!='(' &&ch1!=')'&&ch1!='#'
         {
           i = 0;
           do                          
           {
                z[i++] = ch1;                         //多位数的算术运算例如：(3433+5643)*4532
                ch1 = getchar();                      //do..while()目的把多位数如3433存入字符数组
           }while(ch1>='0' && ch1 <='9' || ch1=='.'); 
            z[i] = '\0';  //字符串结束标志
           push_num(&s_num, atof(z)); //把字符串转换为浮点型数字然后存入数字栈中
       }
     
       else 
         {
         
          switch(compare(&ch2,&ch1))
          {
              case -1: push_flag(&s_flag,ch1);
                       ch1=getchar(); //添加ch1=getchar();
                       break;
              case 0: pop_flag(&s_flag,&ch2);
                      ch1=getchar(); //添加ch1=getchar();    
                      break;
              case 1: pop_flag(&s_flag,&ch2);   //case 1:中ch1已经取得一个大于栈中的字符所以ch1保留该字符
                      pop_num(&s_num,&a);        //而字符栈中弹出一个字符进行运算，运算结果存入数字栈中
                      pop_num(&s_num,&b);        //再从字符栈中取出一个字符ch2与前面保存的ch1比较
                      function(a,ch2,b,&c);        //若ch1<ch2，则case -1:ch1进字符栈,若ch1=ch2,则case 0：ch2出栈（目的是脱括号）
                      push_num(&s_num,c);        //若ch1>ch2,则case 1: 重复上面
                      break;
               default: printf("error");break;  //上面数字运算顺序出错了，function(b, ch2, a, &c);
          }
         }
         gettop_flag(s_flag,&ch2);
        //去掉了 ch1=getchar(); 
}    

printf("%f\n",*(s_num.base));
return 0;    
}