Postfix: An expression is called the postfix expression if the operator appears in the expression after the operands. Simply of the form (operand1 operand2 operator).
Example : AB+CD-* (Infix : (A+B * (C-D) )
Prefix : An expression is called the prefix expression if the operator appears in the expression before the operands. Simply of the form (operator operand1 operand2).
Example : *+AB-CD (Infix : (A+B) * (C-D) )
Given a Postfix expression, convert it into a Prefix expression.
Conversion of Postfix expression directly to Prefix without going through the process of converting them first to Infix and then to Prefix is much better in terms of computation and better understanding the expression (Computers evaluate using Postfix expression).
Input : Postfix : AB+CD-* Output : Prefix : *+AB-CD Explanation : Postfix to Infix : (A+B) * (C-D) Infix to Prefix : *+AB-CD Input : Postfix : ABC/-AK/L-* Output : Prefix : *-A/BC-/AKL Explanation : Postfix to Infix : A-(B/C)*(A/K)-L Infix to Prefix : *-A/BC-/AKL
Algorithm for Prefix to Postfix:
- Read the Postfix expression from left to right
- If the symbol is an operand, then push it onto the Stack
- If the symbol is an operator, then pop two operands from the Stack
Create a string by concatenating the two operands and the operator before them.
string = operator + operand2 + operand1
And push the resultant string back to Stack
- Repeat the above steps until end of Prefix expression.
Prefix : *-A/BC-/AKL
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- Postfix to Infix
- Prefix to Postfix Conversion
- Convert Infix To Prefix Notation
- Stack | Set 2 (Infix to Postfix)
- Prefix to Infix Conversion
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