After you have the appropriate infix to postfix expression how would you do the math with the expression? I'm having difficulty programming it.
// Operator supported: +,-,*,/,%,^,(,)
// Operands supported: all single character operands
#include<stdio.h>
#include<conio.h>
#include<ctype.h>
#define MAX 50
typedef struct stack
{
int data[MAX];
int top;
}stack;
int precedence(char);
void init(stack *);
int empty(stack *);
int full(stack *);
int pop(stack *);
void push(stack *,int);
int top(stack *); //value of the top element
void infix_to_postfix(char infix[],char postfix[]);
void main()
{
char infix[30],postfix[30];
printf("Enter an infix expression(eg: 5+2*4): ");
gets(infix);
infix_to_postfix(infix,postfix);
printf("\nPostfix expression: %s",postfix);
}
void infix_to_postfix(char infix[],char postfix[])
{
stack s;
char x,token;
int i,j; //i-index of infix,j-index of postfix
init(&s);
j=0;
for(i=0;infix[i]!='\0';i++)
{
token=infix[i];
if(isalnum(token))
postfix[j++]=token;
else
if(token=='(')
push(&s,'(');
else
if(token==')')
while((x=pop(&s))!='(')
postfix[j++]=x;
else
{
while(precedence(token)<=precedence(top(&s))&&!empty(&s))
{
x=pop(&s);
postfix[j++]=x;
}
push(&s,token);
}
}
while(!empty(&s))
{
x=pop(&s);
postfix[j++]=x;
}
postfix[j]='\0';
}
int precedence(char x)
{
if(x=='(')
return(0);
if(x=='+'||x=='-')
return(1);
if(x=='*'||x=='/'||x=='%')
return(2);
return(3);
}
void init(stack *s)
{
s->top=-1;
}
int empty(stack *s)
{
if(s->top==-1)
return(1);
return(0);
}
int full(stack *s)
{
if(s->top==MAX-1)
return(1);
return(0);
}
void push(stack *s,int x)
{
s->top=s->top+1;
s->data[s->top]=x;
}
int pop(stack *s)
{
int x;
x=s->data[s->top];
s->top=s->top-1;
return(x);
}
int top(stack *p)
{
return (p->data[p->top]);
}
