DS 4 - INFIX EXPRESSION TO POSTFIX EXPRESSION

4. Design, Develop and Implement a Program in C for converting an Infix Expression to Postfix Expression. Program should support for both parenthesized and free parenthesized expressions with the operators: +, -, *, /, %(Remainder), ^(Power) and alphanumeric operands.

infixtopostfix.c - PROGRAM

#include<stdio.h>
#include<string.h>

int F(char symbol)
{
switch (symbol)
{
case '+':
case '-':return 2;
case '*':
case '/':
case '%':return 4;
case '^':
case '$':return 5;
case '(':return 0;
case '#':return -1;
default :return 8;
}
}

int G(char symbol)
{
switch (symbol)
{
case '+':
case '-':return 1;
case '*':
case '/':
case '%':return 3;
case '^':
case '$':return 6;
case '(':return 3;
case ')':return 0;
default :return 7;
}
}

void infix_postfix(char infix[], char postfix[])
{
int top=-1, j=0, i;
char s[30], symbol;
s[++top] = '#';
for(i=0; i < strlen(infix); i++)
{
symbol = infix[i];
while (F(s[top]) > G(symbol))
{
postfix[j] = s[top--];
j++;
}
if(F(s[top]) != G(symbol))
s[++top] = symbol;
else
top--;
}
while(s[top] != '#')
postfix[j++] = s[top--];
postfix[j] = '\0';
}

void main()
{
char infix[20], postfix[20];
printf("\nEnter a valid infix expression\n") ;
scanf ("%s", infix) ;
infix_postfix (infix, postfix);
printf("\nThe infix expression is:\n");
printf ("%s",infix);
printf("\nThe postfix expression is:\n");
printf ("%s",postfix) ;

}