Page 505 - Computer science 868 Class 12
P. 505

Operator + is        +

                       pushed to stack      (                                                     A B + C D
                                            *
                                            (
                                            /
                       Operand E            +

                       appended with        (                                                    A B + C D E
                       postfix              *
                       expression           (
                                            /
                       Right                )     Closing bracket encountered. All the operators  A B + C D E +
                       parenthesis )        +     till opening parenthesis popped and appended
                       pushed to stack      (     to the postfix expression
                                            *
                                            (
                                            /

                       Right                )     Closing bracket encountered. All the operators  A B + C D E + *
                       parenthesis )        *     till opening parenthesis popped and appended
                       pushed to stack      (     to the postfix expression
                                            /

                       End of scanning      /                                                  A B + C D E + * /


                   b.  Bracket method
                  Ans.  i.  Enclose  the  parts  of  the  expression  between  left  and  right  parenthesis  according  to  the  precedence  of
                        operators.
                     ii.  Express the elements within the brackets in postfix notation.

                                                             (A + B) / (C * (D + E))
                                                             = (AB +) / (C * (D E +))

                                                             = (A B +) / (C D E + *)
                                                             = A B + C D E + * /
                   2.  Convert the following Infix expression to its postfix form.                              [ISC 2011]

                      (A + B * C - D / E)
                   a.   Stack Method

                  Ans.     Scanned symbol                            Stack                         Postfix expression
                       Left parenthesis (
                       pushed to stack          (









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                                                                                                       Data Structures  503
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