expression.c

C表达式计算

#include<stdio.h>
#include<stdlib.h>     
#include<string.h>
#include<conio.h>
#define STACK_INIT_SIZE 100
#define STACKINCREMENT 10
#define ERROR 0
#define OK 1

typedef struct SqStack1
{
 int *base;
 int *top;
 int stacksize;
}SqStack1;

typedef struct SqStack2
{
 char *base;
 char *top;
 int stacksize;
}SqStack2;

void IntInitStack(SqStack1 *S)
{
 S->base=(int *)malloc(STACK_INIT_SIZE*sizeof(int));
 if(!S->base)
  exit(ERROR);
 S->top=S->base;
 S->stacksize=STACK_INIT_SIZE;
}

void CharInitStack(SqStack2 *S)
{
 S->base=(char *)malloc(STACK_INIT_SIZE*sizeof(char));
 if(!S->base)
  exit(ERROR);
 S->top=S->base;
 S->stacksize=STACK_INIT_SIZE;
}

int IntGetTop(SqStack1 *S)
{ 
 int e;
 if((*S).top==(*S).base) return 0;
 e=*((*S).top-1);
 return e;
}

char CharGetTop(SqStack2 *S)
{ 
 char e;
 if((*S).top==(*S).base) return 0;
 e=*((*S).top-1);
 return e;
}

int IntPush(SqStack1 *S,int e)
{
 *(*S).top++=e;
 return OK;
}

int CharPush(SqStack2 *S,char e)
{
 *(*S).top++=e;
 return OK;
}

int IntPop(SqStack1 *S)
{
 int e;
 if((*S).top==(*S).base) return 0;
 e=*--(*S).top;
 return e;
}

int CharPop(SqStack2 *S)
{
 char e;
 if((*S).top==(*S).base) return 0;
 e=*--(*S).top;
 return e;
}
             

char Precede(char a,char b)
{
 int i,j;
 char Table[8][8]={ ' ','+','-','*','/','(',')','#',
     '+','>','>','<','<','<','>','>',
     '-','>','>','<','<','<','>','>',
     '*','>','>','>','>','<','>','>',
     '/','>','>','>','>','<','>','>',
     '(','<','<','<','<','<','=',' ',
     ')','>','>','>','>',' ','>','>',
     '#','<','<','<','<','<',' ','=',
     };
 for(i=0;i<8;i++)
  if(Table[0][i]==a)
   break;
 for(j=0;j<8;j++)
  if(Table[j][0]==b)
   break;
 return Table[j][i];
}

int Operate(int a,char theta,int b)
{
 int c;
 if(theta=='+') c=a+b;
 else if(theta=='-') c=a-b;
 else if(theta=='*') c=a*b;
 else c=a/b;
 return c;
}

int ReadNum(char s)
{
 if(s>=49&&s<=57)
 {
  s-=48;
  return s;
 }
 else
  return 0;
}

int result(char *a,SqStack1 *OPND,SqStack2 *OPTR)
{
 char theta;
 int b,c,i=0;
 IntInitStack(OPND);
 CharInitStack(OPTR);
 CharPush(OPTR,'#');
  while(1)
 { 
  if(ReadNum(a[i]))
   IntPush(OPND,ReadNum(a[i++]));
  else if(a[i]=='+'||a[i]=='-'||a[i]=='*'||a[i]=='/'||a[i]=='#'||a[i]=='('||a[i]==')')
  {
   switch(Precede(a[i],CharGetTop(OPTR)))
   {
   case '<':CharPush(OPTR,a[i++]);break;
   case '=':CharPop(OPTR);i++;break;
   case '>':theta=CharPop(OPTR);
      c=IntPop(OPND);
      b=IntPop(OPND);
      IntPush(OPND,Operate(b,theta,c));
      break;
   }
  }
  if(a[i]=='#'&&CharGetTop(OPTR)=='#')     
  {
   printf("The result is %d.\n",IntGetTop(OPND));
   return OK;
  }
 }
}

char enchange(char *a)
{
 char ch,b[100];
 int i=0,j=0;
 SqStack2 r,*R;
 R=&r;
 CharInitStack(R);
 CharPush(R,'#');
 ch=a[i];
 while(ch!='#')
 {
  if(ch=='(')
  {
   CharPush(R,ch);
   ch=a[++i];
  }
  else if(ch==')')
  {
   if(CharGetTop(R)!='(')
    b[j++]=CharPop(R);
   CharPop(R);
   ch=a[++i];
  }
  else if(ch=='+'||ch=='-'||ch=='*'||ch=='/')
  {
   if(Precede(ch,CharGetTop(R))=='<')
    CharPush(R,ch);
   else 
    b[j++]=CharGetTop(R);
   ch=a[++i];
  }
  else if(ch>=49&&ch<=57)
  {
   ch-=48;
   b[j++]=ch;
   ch=a[++i];
  }
 }
 ch=CharPop(R);
 while(ch!='#')
 {
  b[j]=ch;
  ch=CharPop(R);j++;
 }
 b[j]='#';
 printf("The changed expression is: ");
 for(i=0;b[i]!='#';i++)
 {
  if(b[i]>=1&&b[i]<=9)
   printf("%d",b[i]);
  else 
   printf("%c",b[i]);
 }
 printf(".\n");
 return OK;
}


void main()
{ 
 char a[100];
 SqStack1 s1,*OPND;
 SqStack2 s2,*OPTR;
 OPND=&s1;
 OPTR=&s2;
 printf("enter an expression end of '#'.\n");
 printf("The Expression:");
 scanf("%s",&a);
 result(a,OPND,OPTR);
 getch();
}