bds.cpp

需求分析 (1) 任何一个表达式都是由操作数、运算符和界限符组成的,我们称之为单词. (2) 表达式求值首先要符合四则运算规则: ① 先乘除,后加减 ② 从左到右进行运算 ③ 先括号内,后括

#include "stdio.h"
#include "malloc.h"
#include "stdlib.h"
#define M 100

int m;
void push1(char a[100],char e,int top)  //把字符押入栈//
{
   a[top]=e;
   return;

}

void  push2(int b[100],int e,int top)  //把字符押入栈//
{
    b[top]=e;
	return;

}
              
int operate (int a,char theta,int b)    //A和B做运算//
{  
    switch (theta)
	{
	     case '+' : m=a+b; break;
		 case '-' : m=a-b; break;
         case '/' : m=a/b; break;
         case '*' : m=a*b; break;
		default :printf ("error\n");
	}
	return(m); 
}

int precede(char c,char d)    //运算符做比较//
{   int I,J,f;
    int p,q;
    int a[6]={5,4,2,0,7,0};
	int b[6]={6,3,1,7,0,0};
  	switch(c)
	{
	            case '^' : I=0;  break;
	            case '*' : I=1;  break;
	            case '/' : I=1;  break;
	            case '+' : I=2;  break;
	            case '-' : I=2;  break;
	            case '(' : I=3;  break;
	            case ')' : I=4;  break;
	            case '#' : I=5;  break;
	            default :printf ("error\n");
	}
         p=I;
		
         switch(d)
		 {
	            case '^' : J=0;  break;
	            case '*' : J=1;  break; 
	            case '/' : J=1;  break;  
	            case '+' : J=2;  break; 
	            case '-' : J=2;  break; 
	            case '(' : J=3;  break;
	            case ')' : J=4;  break;
	            case '#' : J=5;  break;
	            default : printf ("error\n");
		 }
		 q=J;
		 
	
	return( f= a[p]-b[q]);
  
		
}

void main()
{  
   int A;
   int J,I,n;
   int top1,top2; //栈顶指针
   int i,j,k;
   char str1[M];
   char f,u;
   char str[3];
   int h1,h2,h3,h4;
   char r,s;
   char a[100];
   int b[100];
   char c[100],d[100];
   int F;
   char theta;
   int p,q;
   printf("请输入表达式(以#号结束):\n");
   scanf("%s",str1);
   top1=0;    top2=0;
   push1(a,'#',top1);
   top1++;
   push2(b,0,top2);
   top2++;
   r='#';  J=0;
   for(i=0;(f=str1[i])!='\0';i++)
   {  j=0; k=0;
      if (((f=str1[i])!= '0') && ((f=str1[i])!= '1') && ((f=str1[i])!= '2') && ((f=str1[i])!= '3' )&&((f=str1[i])!= '4' )&&((f=str1[i])!= '5' )&&((f=str1[i])!= '6' )&&((f=str1[i])!= '7' )&&((f=str1[i])!= '8')&& ((f=str1[i])!= '9'))
	  {
		  while (((f=str1[i])!= '+' )&& ((f=str1[i])!='-') && ((f=str1[i])!='*') && ((f=str1[i])!='/') && ((f=str1[i])!='(') && ((f=str1[i])!=')') && ((f=str1[i])!='^') && ((f=str1[i])!='#'))
		  {
		  i++;
              if (((f=str1[i])!='+') && ((f=str1[i])!='-') && ((f=str1[i])!='*') && ((f=str1[i])!='/') && ((f=str1[i])!='(') && ((f=str1[i])!=')') && ((f=str1[i])!='^') && ((f=str1[i])!='#') ) 
			  {    --i;
			       str[j]=str1[i];
		           j++;  i++;
			       str[j]=str1[i];
			  }
		      else if ((((f=str1[i])=='+') || ((f=str1[i])=='-') ||((f=str1[i])=='*') || ((f=str1[i])=='/') || ((f=str1[i])=='(') || ((f=str1[i])==')') || ((f=str1[i])=='^') || ((f=str1[i])=='#')) && j==0)
			  {   
			     --i;
			     u=str1[i];
			     printf("请输入%c的值:%c=",u,u);
		         scanf("%d",&h1);
			     push2(b,h1,top2);
			     top2++;
			     i++;
			  }
		      else if((((f=str1[i])=='+') || ((f=str1[i])=='-') || ((f=str1[i])=='*') ||((f=str1[i])=='/') || ((f=str1[i])=='(') || ((f=str1[i])==')') || ((f=str1[i])=='#') || ((f=str1[i])=='^')) && j>0)
			  {   
			  
			     printf ("请输入值");
			     str[j+1]='\0';
			     printf("%s=",str);
			     scanf ("%d",&h2);
			     push2(b,h2,top2);
			     top2++;
			     j=0;
			  }
		  }
	  }
	  else 
	  {  
		  while (((f=str1[i])!= '+' )&& ((f=str1[i])!='-') && ((f=str1[i])!='*') && ((f=str1[i])!='/') && ((f=str1[i])!='(') && ((f=str1[i])!=')') && ((f=str1[i])!='^') && ((f=str1[i])!='#'))
		  {
		      i++;
              if (((f=str1[i])!='+') && ((f=str1[i])!='-') && ((f=str1[i])!='*') && ((f=str1[i])!='/') && ((f=str1[i])!='(') && ((f=str1[i])!=')') && ((f=str1[i])!='^') && ((f=str1[i])!='#') ) 
			  {    --i;
			      c[k]=str1[i];
		           k++;  i++;
			       c[k]=str1[i];
			  }
		      else if ((((f=str1[i])=='+') || ((f=str1[i])=='-') ||((f=str1[i])=='*') || ((f=str1[i])=='/') || ((f=str1[i])=='(') || ((f=str1[i])==')') || ((f=str1[i])=='^') || ((f=str1[i])=='#')) && k==0)
			  {   
			      --i;
			       d[0]=str1[i];
			      h3=atoi(d);
			      push2(b,h3,top2);
			      top2++;
			      i++;
			  }
		      else if((((f=str1[i])=='+') || ((f=str1[i])=='-') || ((f=str1[i])=='*') ||((f=str1[i])=='/') || ((f=str1[i])=='(') || ((f=str1[i])==')') || ((f=str1[i])=='#') || ((f=str1[i])=='^')) && k>0)
			  {   
			  
			        c[k+1]='\0';
			         h4=atoi(c);
			        push2(b,h4,top2);
			         top2++;
			         k=0;
			  }
		  }
	   }
	   s=str1[i];
       if (r!='#')
	   {   
		   F=precede(r,s);
		   if(F<0)
		   {
			   r=s;
		       push1(a,r,top1);
			   top1++;
			   
		   }
           else if (F==0)
		   {	
			  top1--;
			  r=a[top1];
		   }
		   else 
		   {
			   
			   theta=r;
			   top2--;
			   p=b[top2];
			   top2--;
			   q=b[top2];
			   if (r=='^')
			   {   
				   n=q;
				   for (I=1;I<p;I++)
					   n=n*q;
				       m=n;
			   }
			   else 
			   {
				   m=operate(q,theta,p);
			   }
			   push2(b,m,top2);
			   top2++;
			   top1--;
			   top1--;
			   r=a[top1];
			   top1++;
               J=0;
			   while(r!='#' && J==0)
			   {
			        F=precede(r,s);
		              if(F<0)
					  {
			           r=s;
		               push1(a,r,top1);
			           top1++;
			           J=1;
					  }
                      else if (F==0)
					  {	
			            top1--;
					    top1--;
			            r=a[top1];
						top1++;
						J=1;
					  }
		             else 
					 {  
						 theta=r;
                         top2--;
			             p=b[top2];
			             top2--;
			             q=b[top2];
                         if (r=='^')
						 {   
				             n=q;
				             for (I=1;I<p;I++)
					         n=n*q;
				             m=n;
						 }
			             else 
						 {
				             m=operate(q,theta,p);
						 } 
			              push2(b,m,top2);
			              top2++; 
						  top1--;
			              top1--;
			              r=a[top1];
						  top1++;
			             
					 }
			   }
		}

	}

	  if (r=='#' && s!='#')
	  {
		r=s;
		push1(a,r,top1);
		top1++;
	
	  }
     else if(r!='#' && s!='#' && s!=')')
	 {
		 r=s;
	 }
	 else if (r=='#' && s=='#')
	 {  
	   printf("最后的结果是：");
       printf("%d",m);
       printf("\n");
	 }
	 else 
		A=1;
   }
}