表达式计算

#include <stdio.h>
# include "G:expressmystack.h"

char piror[7][7]={'>','>','<','<','<','>','>',
                  '>','>','<','<','<','>','>',
			      '>','>','>','>','<','>','>',
			      '>','>','>','>','<','>','>',
			      '<','<','<','<','<','=','f',
			      '>','>','>','>','f','>','>',
			      '<','<','<','<','<','f','='};


int chartoint(char ch)
{
	switch(ch)
	{
		case '+':return 0;
		case '-':return 1;
		case '*':return 2;
		case '/':return 3;
		case '(':return 4;
		case ')':return 5;
		case '#':return 6;
	}
}

int numchar(char ch)
{
	if (ch>='0' && ch<='9')
		return 1;
	else return 0;
}

int isoptr(char ch)
{
	switch(ch)
	{
		case '+':
		case '-':
		case '*':
		case '/':
		case '(':
		case ')':
		case '#':return 1;
		default :return 0;
	}
}

float operate(float n1,char ch,float n2)
{
	switch(ch)
	{
		case '+':return n1+n2;
		case '-':return n1-n2;
		case '*':return n1*n2;
		case '/':return n1/n2;
	}
}

main()
{
   char str[80];
   gets(str);
   int i=0;
   int number1,exp10;
   char ch1,ch2,curroptr1;
   float number,number2,n1,n2,n3,curroptr,ch3;

   sqstack optr,opnd;
   initstack(optr);push(optr,'#');
   initstack(opnd);

   while(str[i]!='')
   {
	   number1=0;
	   while(numchar(str[i]))
	   {
		   number1=number1*10+(str[i]-'0');
		   i++;
	   }
	   //已经读取了一个整数
	   printf("number1_________uuuu=%d
",number1);
       if (str[i]=='.')
	   {
		   i++;
		   number2=0.0;exp10=10;
	       while(numchar(str[i]))
		   {
			   number2=number2+((str[i]-'0')*1.0)/exp10;
			   exp10=exp10*10;
			   i++;
			   //printf("number2=%f
",number2);
		   }
		   number=number1+number2;
		   printf("number_float=%f
",number);
		   push(opnd,number);
	   }

       push(opnd,number1);
	   printf("number_int=%d
",number1);

       if(!isoptr(str[i]))
	   {
		   printf("express error---1!
");
		   exit(0);
	   }
       ch1=(char)gettop(optr);
	   ch2=str[i];
	   printf("ch1=%c,ch2=%c
",ch1,ch2);
       
	   if(piror[chartoint(ch1)][chartoint(ch2)]=='>')
	   {
		while(piror[chartoint(ch1)][chartoint(ch2)]=='>')	 
		{
			pop(opnd,n2);
		     pop(opnd,n1);
			 pop(optr,curroptr);
             curroptr1=(char)curroptr;
             printf("
---%f %c %f=====%f
",n1,curroptr1,n2,operate(n1,curroptr1,n2));
             push(opnd,operate(n1,curroptr1,n2));
             ch1=(char)gettop(optr);
		}
        push(optr,ch2);
	   }
	   else if(piror[chartoint(ch1)][chartoint(ch2)]=='<') push(optr,ch2);
	   else if(piror[chartoint(ch1)][chartoint(ch2)]=='=') pop(optr,ch3);
	   else
			 {
		        printf("express error---2!
");
		        exit(0);
			 }
      i++;
   }
   pop(opnd,n3);
   printf("result=%f
",n3);
}

　　

#include <stdlib.h>
#include <stdio.h>

#define stackinitsize 50
#define stackincrement 8

typedef float elemtype;

typedef struct{
  elemtype *base;
  elemtype *top;
  int stacksize;
}sqstack;


int  initstack(sqstack &s)
  {s.base=(elemtype * ) malloc(stackinitsize*sizeof(int));
   s.top=s.base;
   s.stacksize=stackinitsize;
   return 1;
   }

int push(sqstack &s,elemtype e)
 {
   *(s.top)=e;
   s.top++;
   return 1;
 }

elemtype gettop(sqstack s)
{
  return *(s.top-1);
 }

int emptystack(sqstack s)
  {if (s.top==s.base)  return 1;
   else return 0;
   }

int pop(sqstack &s,elemtype &e)
   { if (emptystack(s)) return 0;
     --s.top;
     e=*(s.top);
    return 1;
     }