int main()
{
int i=0,j=0,x,item;
printf("enter infix expression\n");
gets(inexp);
// puts(inexp);
item=inexp[i];i++;
while(item!='\0')
{
if(item=='(')
{
push(item);
}
else if((item>='A'&&item<='Z')||(item>='a'&&item<='z'))
{
postexp[j]=item;j++;
}
else if(isop(item)==1)
{
x=pop();
while(isop(x)==1&&(preced(x)>=preced(item)))
{
postexp[j]=x;j++;
x=pop();
}
push(x);
push(item);
}
else if(item==')')
{
x=pop();
while(x!='(')
{
postexp[j]=x;
j++;
x=pop();
}
}
else
{
printf("\ninvalid arithmetic expression");
}
item=inexp[i];
i++;
}
x=pop();
while(x!='a')
{
postexp[j]=x;
j++;
x=pop();
}
postexp[j++]='\0';
printf("\npostfix expression\n");
puts(postexp);
getch();
return 0;
}
void main()
{
char str[100],temp;
int len,inp_ptr=0,f,prec,no;
printf("\nEnter the expression :");
scanf("%s",str);
push('$');
len=strlen(str);
str[len]='$';
str[len+1]='\0';
puts(str);
while(str[inp_ptr]!='$'|| peek()!='$')
{
f=0;
printf("\nin the while");
if(str[inp_ptr]>='0'&&str[inp_ptr]<='9'){
no=atoi(&str[inp_ptr++]);
printf("#####%d###",no);
while(str[inp_ptr]<='0'&&str[inp_ptr]>='9')
inp_ptr++;
str[inp_ptr--]='i';
f=1;
}
prec=preced(peek(),str[inp_ptr]);
printf("@@%d@@",prec);
printf("reached here1");
if(prec==0)
{
if(f==1)
pushres(no);
push(str[inp_ptr++]);
}
else if(prec==1)
{
do{
temp=pop();
printf("reached here<F2>");
switch(temp){
case '+': pushres(popres()+popres());break;
case '*': pushres(popres()*popres());break;
}
}while(preced(peek(),temp)!=0);
}
else
error();
}
printf("Result=%d\n",popres());
}
void in_to_post(char infix[])
{
int length;
static int index=0,pos=0;
char symbol,temp;
char postfix[40];
length=strlen(infix);
push('#');
while(index<length)
{
symbol=infix[index];
switch(symbol)
{
case'(':push(symbol);
break;
case')' :temp=pop();
while(temp!='(')
{
postfix[pos]=temp;
pos++;
temp=pop();
}
break;
case '+' :
case '-' :
case '*' :
case '/' :
case '^' :
while (preced(stack[top])>=preced(symbol))
{
temp=pop();
postfix[pos]=temp;
pos++;
}
push(symbol);
break;
default : postfix[pos++]=symbol;
break;
}
index++;
}
while(top>0)
{
temp=pop();
postfix[pos++]=temp;
}
postfix[pos++]='\0';
puts(postfix);
return;
}
