notes printf"\ts pushing % \ "op )spushsop )breakbool isopchar op /is op an operator*return (getindex(op!- )char *in prechar *str /returns valid infix expr in str to prefix *char *sptrqueue {null}stack nullchar *res (char *)mallocn*sizeof(char)char *resptr restptr tforsptr=str+strlen(str)- sptr!=str- -sptr printf"processing % tptr- =% \ "*sptrtptr- )ifisalpha(*sptr/if operand qpush& *sptr )else ifisop(*sptr/if valid operator processop*sptr& & )else ifisspace(*sptr/if whitespace else fprintfstderr"error:invalid char % \ "*sptr )return ""while!qempty(& *tptr+qpop(& )printf"\tq popping % \ "*(tptr- )while!sempty(& *tptr+spop(& )printf"\ts popping % \ "*(tptr- )contd lovely professional university