整数中缀表达式求值

#include<stdio.h>

#include<stdlib.h>

#define MAX 50

typedef struct

{

       char data[MAX];

       int top;

}stack;

typedef struct

{

       float data[MAX];

       int top;

}fstack;stack* create()

{

       stack *s;

       s=malloc(sizeof(stack));

       s->top=-1;

       return s;

}

fstack* fcreate()

{

       fstack *s;

       s=malloc(sizeof(fstack));

       s->top=-1;

       return s;

}

int getstack(stack *s,char x )

{

       if(s->top==MAX-1)

              return 0;

       s->top++;

       s->data[s->top]=x;

       return 1;

}

int fgetstack(fstack *s,float x )

{

       if(s->top==MAX-1)

              return 0;

       s->top++;

       s->data[s->top]=x;

       return 1;

}

int outstack(stack *s,char *x)

{

       if(s->top==-1)

              return 0;

       *x=s->data[s->top];

       s->top--;

       return 1;

}

int foutstack(fstack *s,float *x)

{

       if(s->top==-1)

              return 0;

       *x=s->data[s->top];

       s->top--;

       return 1;

}

char readstack(stack *s)

{

       char x;

       if(s->top==-1)

              return '0';

       x=s->data[s->top];

       return x;

}

float freadstack(fstack *s)

{

       float x;

       if(s->top==-1)

              return '0';

       x=s->data[s->top];

       return x;

}

char bi(char x1,char x2)//>出站；<进站；

{

       switch(x1)

       {

       case '(':

              switch(x2)

              {

              case ')':

                     return '>';

                     break;

              default:

                     return '<';

                     break;

              }

              break;

       case '+':

       case '-':

              switch(x2)

              {

              case '(':

                     return '<';

                     break;

              case '*':

                     return '<';

                     break;

              case '/':

                     return '<';

                     break;

              default :

                     return '>';

              }break;

       case '*':

       case '/':

              switch(x2)

              {

              case '(':

                     return '<';

                     break;

              default :

                     return '>';

              }break;

       }

       return '0';

}

float jisuan(float x1,char a,float y1)

{

       switch(a)

       {

       case '+':

              return x1+y1;

       case '-':

              return x1-y1;

       case '*':

              return x1*y1;

       case '/':

              return x1/y1;

       }

       return 0;

}

float fun1(char a[])

{

       float b,b1,b2,b3;

       int i=0;

       char x,x1,ch;  

       stack *s=create();

       fstack *p=fcreate();

       getstack(s,'(');

       ch=a[0];

       while(ch!='#')

       {    

              switch(ch)

              {

              case '(':

                     getstack(s,'(');

                     break;

              case ')':

                     while(readstack(s)!='(')

                     {

                            outstack(s,&x);

                            foutstack(p,&b1);

                            foutstack(p,&b2);

                            b3=jisuan(b1,x,b2);

                            fgetstack(p,b3);

                     }

                     outstack(s,&x);

                     break;

              case '+':

              case '-':

                     x=readstack(s);

                     x1=bi(x,ch);

                     if(x1=='<')

                            getstack(s,ch);

                     else

                     {

                            while(readstack(s)!='(')

                            {

                                   outstack(s,&x);

                                   foutstack(p,&b1);

                                   foutstack(p,&b2);

                                   b3=jisuan(b1,x,b2);

                                   fgetstack(p,b3);

                            }

                            getstack(s,ch);

                     }    

                     break;

              case '*':

              case '/':

                     x=readstack(s);

                     x1=bi(x,ch);

                     if(x1=='<')

                            getstack(s,ch);

                     else

                     {

                            while(readstack(s)!='('&&readstack(s)!='+'&&readstack(s)!='-')

                            {

                                   outstack(s,&x);

                                   foutstack(p,&b1);

                                   foutstack(p,&b2);

                                   b3=jisuan(b1,x,b2);

                                   fgetstack(p,b3);

                            }

                            getstack(s,ch);

                     }    

                     break;

              default :

                     if(ch>='0'&&ch<='9')

                     {

                            fgetstack(p,(ch-'0'));

                            printf("%f\n",freadstack(p));

                     }

                     break;

              }

       ch=a[++i];     

       }

       while(readstack(s)!='(')

       {

              outstack(s,&x);

              foutstack(p,&b1);  

              foutstack(p,&b2);

              b3=jisuan(b1,x,b2);

              fgetstack(p,b3);

       }

       b=freadstack(p);

 

       return b;

}

int main()

{

       int i;

       float b;

       char a[MAX];

       for(i=0;;i++)

       {

              scanf("%c",&a[i]);

              if(a[i]=='#')

                     break;

       }

       b=fun1(a);

       printf("====%f\n",b);

}