Write a program to convert the given infix expression into its postfix form

#include

#include

#include

#include

int TOP = -1, rank = 0;

char STACK[50];

class infix_exp

{

public:

void PUSH(char item);

char POP();

int F(char symbol);

int G(char symbol);

int RANK(char symbol);

int infix_postfix(char infix[ ], char postfix[ ]);

};

void infix_exp::PUSH(char item)

{

TOP++;

STACK[TOP] = item;

}

char infix_exp::POP()

{

return STACK[TOP--];

}

int infix_exp::F(char symbol)

{

switch (symbol)

{

case '+':

case '-': return 1;

case '*':

case '/': return 3;

case '^': return 6;

case '(': return 9;

case ')': return 0;

default: return 7;

}

}

int infix_exp::G(char symbol)

{

switch (symbol)

{

case '+':

case '-': return 2;

case '*':

case '/': return 4;

case '^': return 5;

case '(': return 0;

case '#': return -1;

default: return 8;

}

}

int infix_exp::RANK(char symbol)

{

switch (symbol)

{

case '+':

case '-':

case '*':

case '/':

case '^': return -1;

default: return 1;

}

}

int infix_exp::infix_postfix(char infix[50], char postfix[50])

{

int length, i, j = 0;

char ch, temp;

length = strlen(infix);

PUSH('#');

for (i=0 ;i

{

ch = infix[i];

while (F(ch)

{

temp = POP();

rank += RANK(temp);

if (rank<1 font="font">

{

return -1;

}

postfix[j++] = temp;

}

if (F(ch)!=G(STACK[TOP]))

{

PUSH(ch);

}

else

POP();

}

while (STACK[TOP]!='#')

{

temp = POP();

rank += RANK(temp);

if (rank<1 font="font">

{

return -1;

}

postfix[j++] = temp;

}

postfix[j] = '\0';

return rank;

}

void main()

{

char infix[50], postfix[50];

infix_exp obj;

clrscr();

cout << "\nEnter a valid infix expression : " ;

gets(infix);

rank = obj.infix_postfix(infix, postfix);

if (rank==1)

{

cout << "\nPostfix expression is : " << postfix;

}

else

cout << "\nInvalid infix expression" ;

getch();

}