简单表达式求值

 

此表达式求值程序利用Stack实现

/**//******************************
Date: 
     2006 - 10 -24
Description:
 This programe is aiming to
 carry out operator counting by
 using of sequence stack
*******************************/
#include "stdio.h"
#define MAXSIZE 128
typedef char DataType;
int pIFX = 0;
int pPFX = 0;
int pTP = 0;

/**//***Define a Stack Struct***/
typedef struct 
...{
        DataType stack[MAXSIZE];
        }SeqStack;
/**//**********初始化PFX IFX************/

SeqStack PFX;
SeqStack IFX;
SeqStack TP;

/**//***************************
Function: Stack push
Param:    SeqStack ss, char dat
Return:   SeqStack
****************************/
SeqStack Push(SeqStack s, char dat)
...{
         s.stack[pPFX] = dat;
         return s;
         
         }              
/**//***************************
Function: Stack pop
Param:    SeqStack ss, char dat
Return:   SeqStack
****************************/
SeqStack Pop(SeqStack s, char dat)
...{
         
}
int CtoD(char c)
...{
    return(c - '0');
}
char DtoC(int x)
...{
    return(x + 48);
}               

char InputPression(void)
...{
     int i = 0;
     char ch;
     scanf("%c",&ch);
     while(ch!= '=')
     ...{
          IFX.stack[i ++] = ch;
          scanf("%c",&ch);          
     }
     IFX.stack[i] = '=';

}   
 
void PrintStack(SeqStack s)
...{
      int i = 0;
      while(s.stack[i] != '=')
      printf("%c",s.stack[i++]);
      getchar();
      getchar();
     }  
SeqStack toSufix()
...{
     int pIFX = 0;
     char ch;
     TP.stack[pTP++] = '=';
     while(IFX.stack[pIFX]!= '=')
     ...{
         ch = IFX.stack[pIFX];
         switch(ch)
         ...{
              case '0':case '1':case '2':case '3':
              case '4':case '5':case '6':case '7':
              case '8': case'9':
                   PFX.stack[pPFX++] = ch;
                   
                   break;
              case '(':
                   TP.stack[++pTP] = '(';
                   
                   break;
              case ')':
                   while(TP.stack[pTP] != '(')
                   ...{
                       PFX.stack[pPFX++] = TP.stack[pTP];
                       pTP--;
                   }
                   pTP--;
                 
                   break;
              case '+':
              case '-':
                   while(
                   (pTP > 1 && TP.stack[pTP] != '(') &&
                   (TP.stack[pTP]== '+' || TP.stack[pTP]== '-')
                   )
                   PFX.stack[pPFX++] = TP.stack[pTP--];
                   pTP ++;
                   TP.stack[pTP]= ch;
                   
                   break;
               case '*':
               case '/':
                    while(
                    pTP > 1 && 
                    (TP.stack[pTP]== '*' || TP.stack[pTP]== '/')
                    )
                    PFX.stack[pPFX++] = TP.stack[pTP--];
                    pTP++;
                    TP.stack[pTP] = ch;
                    
                    break;    
                    }/**//*end switch*/  
                pIFX++;              
     }/**//*end while*/
     while(pTP > 1)
     PFX.stack[pPFX++] = TP.stack[pTP--];
     PFX.stack[pPFX] = '=';
}
int Computing()  
...{
    char ch;
    char tmp1;
    char tmp2;
    int tmp;
    pPFX = 0;
    pIFX = 0;
    pTP = 0;
    while(PFX.stack[pPFX]!= '=')
    ...{
        ch = PFX.stack[pPFX];
        switch(ch)
        ...{
            case '0':case '1':case '2':case '3':
            case '4':case '5':case '6':case '7':
            case '8': case'9':
               pTP++;
               TP.stack[pTP] = ch;
               break; 
            case '+':
                tmp1 = TP.stack[pTP--];
                tmp2 = TP.stack[pTP--];
                tmp = CtoD(tmp1) + CtoD(tmp2);
                TP.stack[++pTP] = DtoC(tmp);
                break;
            case '-':
                tmp1 = TP.stack[pTP--];
                tmp2 = TP.stack[pTP--];
                tmp = CtoD(tmp1) - CtoD(tmp2);
                TP.stack[++pTP] = DtoC(tmp);
                break;
            case '*':
                tmp1 = TP.stack[pTP--];
                tmp2 = TP.stack[pTP--];
                tmp = CtoD(tmp1) * CtoD(tmp2);
                TP.stack[++pTP] = DtoC(tmp);
                break;
            case '/':
                tmp1 = TP.stack[pTP--];
                tmp2 = TP.stack[pTP--];
                tmp = CtoD(tmp1) / CtoD(tmp2);
                TP.stack[++pTP] = DtoC(tmp);
                break;
                
        }/**//*end switch*/
        pPFX ++;
    }/**//*end while*/
    return(CtoD(TP.stack[1]));
}


/**//******************************
   Main Function
*******************************/        
int main()
...{
    printf("Input count pression: ");
    InputPression();
    PrintStack(IFX);
    PFX = toSufix();
    PrintStack(PFX);
    printf("%d",Computing());
    getchar();
}
        

 未完成...