Question

Convert the following infix notations to postfix notations, showing stack and string contents at following step.

A + B - C * D

Answer 1

Infix Expression is : A + B - C * D

Scanning from Left to Right

Symbol	Action	Stack, Initially Stack is Empty [ ]	Postfix Expressions
A	Append to Postfix Expression	[ ]	A
+	PUSH(‘+’)	+	A
B	Append to Postfix Expression	+	A B
–	– have equal precedence to +. First POP(‘+’) then PUSH(‘-‘)	–	A B +
C	Append to Postfix Expression	–	A B + C
*	* have higher precedence than -, PUSH ‘*’	– *	A B + C
D	Append to Postfix Expression	– *	A B + C D
End of Expression	POP all and add to Postfix Expression	[ ]	A B + C D * –

Postfix Expression is : A B + C D * –