/* Program to convert infix expression to postfix expression */
#include
#include
int prec(char ch)
{
switch(ch)
{
case '(':return 0;
case '^':return 3;
case '*':
case '/':return 2;
case '+':
case '-':return 1;
}
}
char pop(char st[],int *top)
{
return(st[(*top)--]);
}
void push(char st[],int *top,char item)
{
st[++(*top)]=item;
}
void in_to_post(char infx[], char postfx[])
{
int i,j,l,top=-1;
char st[20],ch,x;
l=strlen(infx);
infx[l]=')';
push(st,&top,'(');
j=0;
for(i=0;i<=l;i++)
{
ch=infx[i];
switch(ch)
{
case'(':
push(st,&top,ch);
break;
case'^':
push(st,&top,ch);
break;
case'*':
case'/':
case'+':
case'-':
while(prec(ch)<=prec(st[top]))
{
postfx[j++]=pop(st,&top);
}
push(st,&top,ch);
break;
case ')':
while((x=pop(st,&top))!='(')
{
postfx[j++]=x;
}
break;
default: postfx[j++]=ch;
}
}
postfx[j]='\0';
}
main()
{
printf("\nProgram to convert infix expression to postfix expression : \n");
char infx[20],postfx[20];
printf("\nEnter the infix expression:");
scanf("%s",infx);
printf("\nThe infix exp.: %s",infx);
in_to_post(infx,postfx);
printf("\n");
printf("\nThe postfix exp.: %s",postfx);
printf("\n\n");
}
