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 Postfix to Prefix:
- 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.
Below is the implementation of the above idea:
Prefix : *-A/BC-/AKL
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- Prefix to Postfix Conversion
- Infix to Prefix conversion using two stacks
- Prefix to Infix Conversion
- Stack | Set 4 (Evaluation of Postfix Expression)
- Postfix to Infix
- Infix to Postfix using different Precedence Values for In-Stack and Out-Stack
- Stack | Set 2 (Infix to Postfix)
- Case conversion (Lower to Upper and Vice Versa) of a string using BitWise operators in C/C++
- Print all substring of a number without any conversion
- Program for Binary To Decimal Conversion
- Program for Decimal to Binary Conversion
- Program for decimal to hexadecimal conversion
- Decimal to binary conversion without using arithmetic operators
- Program for Celsius To Fahrenheit conversion
- Decimal to octal conversion with minimum use of arithmetic operators
- Number from a range [L, R] having Kth minimum cost of conversion to 1 by given operations
- Gray to Binary and Binary to Gray conversion
- Longest Common Prefix using Word by Word Matching
- Longest Common Prefix using Character by Character Matching
- Longest Common Prefix using Divide and Conquer Algorithm
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