Conversion of infix to postfix expression

# include< stdio.h>

# include< stdlib.h>

struct link

{

char ch;

struct link *next;

};

struct link * pop2(struct link *rec)

{

char ch='a';

struct link *temp;

char x;

while((ch!='(')&&(rec!=NULL))

{

x=rec->ch;

if(x!='(')

printf("%c",x);

temp=rec->next;

free(rec);

rec=temp;

}

return rec;

}

struct link * pop(struct link *rec)

{

if(rec != NULL)

{

struct link *temp;

char x;

x=rec->ch;

if(x!='(')

printf("%c",x);

temp=rec->next;

free(rec);

rec=temp;

}

return rec;

}

struct link * pop1(char z,struct link *rec)

{

struct link *temp;

char x;

x=rec->ch;

if(((x=='+')||(x=='-'))&&((z=='*')||(z=='/')||(z=='%')))

{

}

else

{

if(x!='(')

printf("%c",x);

temp=rec->next;

free(rec);

rec=temp;

}

return rec;

}

struct link *push(char c,struct link *rec)

{

if(c==')')

{

rec=pop2(rec);

}

if((rec!=NULL)&&(c!='('))

{

rec=pop1(c,rec);

}

if(c!=')')

{

struct link *new1;

new1 = (struct link *)malloc(sizeof(struct link));

new1->ch=c;

new1->next = rec;

rec = new1;

}

return rec;

}

void main()

{

struct link *start ;

int i=0;

char ch='a';

clrscr();

start = NULL;

printf("\nEnter the expression:-");

while(ch!='\n')

{

ch=getchar();

if((ch=='+')||(ch=='-')||(ch=='*')||(ch=='/')||(ch=='(')||(ch=='%')||(ch==')'))

{

start=push(ch,start);

i++;

}

else

{

if(ch!='\n')

printf("%c",ch);

}

}

while(i>0)

{

start=pop(start);

i--;

}

getch();

}