算术表达式求值
写了一个算术表达式求值的代码各位给指点下能否再精简点
#include<stdlib.h>
#include<stdio.h>
#define stack_init_size1 40
#define stack_init_size2 20
#define stackincrement1 40
#define stackincrement2 20
typedef struct{
int *base;
int *top;
int stacksize;
}s_stack;
typedef struct{
char *base;
char *top;
int stacksize;
}f_stack;
static char youxian[7][7]=
{ // '+' '-' '*' '/' '(' ')' '#'
{'>','>','<','<','<','>','>'},
{'>','>','<','<','<','>','>'},
{'>','>','>','>','<','>','>'},
{'>','>','>','>','<','>','>'},
{'<','<','<','<','<','=','>'},
{'>','>','>','>','>','>','>'},
{'<','<','<','<','<','>','='}
};
int in(char c)
{
switch(c)
{
case '+': return 0;
case '-': return 1;
case '*': return 2;
case '/': return 3;
case '(': return 4;
case ')': return 5;
case '#':return 6;
default:return 9;
}
}
void s_push(s_stack *s,int e)
{
if(s->top-s->base>=s->stacksize)
{
s->base=(int *)realloc(s->base,(s->stacksize+stackincrement1)*sizeof(int));
if(!s->base) exit(0);
s->top=s->base+s->stacksize;
s->stacksize+=stackincrement1;
}
*s->top=e; s->top++;
/*printf("the s_stack has the data:%d\n",*(s->top-1));*/
}
void f_push(f_stack *f,char e)
{
if(f->top-f->base>=f->stacksize)
{
f->base=(char *)realloc(f->base,(f->stacksize+stackincrement2)*sizeof(char));
if(!f->base) exit (0);
f->top=f->base+f->stacksize;
f->stacksize+=stackincrement2;
}
*f->top=e;f->top++;
/* printf("the f_stack has the sign:%c\n",*(f->top-1));*/
}
int s_gettop(s_stack *s)
{
s->top--;
return *s->top;
}
char f_gettop(f_stack *f)
{
f->top--;
return *f->top;
}
char panduan(f_stack *f,char c)
{
int m,n;
char w;
m=in(c);
w=*(f->top-1);
n=in(w);
return youxian[n][m];
}
int yunsuan(int p,char r,int q)
{
switch(r)
{
case '+': return q+p;
case '-': return q-p;
case '*': return q*p;
case '/': return q/p;
}
}
int main()
{
int h=0,jieguo,wrong;
char c;
s_stack s;
f_stack f;
s.base=(int*)malloc(stack_init_size1*sizeof(int));
if(!s.base) return 0;
s.top=s.base;
s.stacksize=stack_init_size1;
f.base=(char*)malloc(stack_init_size2*sizeof(char));
if(!f.base) return 0;
f.top=f.base;
f.stacksize=stack_init_size2;
*f.top='#';f.top++;
printf("please press the shizi end by enter!\n");
c=getchar();
while(c!='\n')
{ int t;
int p,q;
char r;
if(in(c)==9)
{ if(h>0)
{
t=s_gettop(&s);
s_push(&s,t*10+c-48);
}
else
s_push(&s,c-48);
h++;
c=getchar();
}
else
switch(panduan(&f,c))
{
case '<':
f_push(&f,c);c=getchar();h=0;break;
case '=':
f.top--;
f.stacksize--;
c=getchar();h=0;break;
case '>':
p=s_gettop(&s);
q=s_gettop(&s);
r=f_gettop(&f);
if(r=='/'&&p==0)
{wrong=1;break;}
else
{ jieguo=yunsuan(p,r,q);
s_push(&s,jieguo);h=0;break;
}
}
}
while((c=='\n')&&(*(f.top-1)!='#'))
{
int p,q;
char r;
p=s_gettop(&s);
q=s_gettop(&s);
r=f_gettop(&f);
if(r=='/'&&p==0)
{wrong=1;break;}
else
jieguo=yunsuan(p,r,q);
s_push(&s,jieguo);
}
if(wrong==1)
printf("It is wrong!\n");
else
printf("the answer is %d\n",s_gettop(&s));
}
