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) )
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) )
Given a Prefix expression, convert it into a Postfix expression.
Conversion of Prefix expression directly to Postfix without going through the process of converting them first to Infix and then to Postfix is much better in terms of computation and better understanding the expression (Computers evaluate using Postfix expression).
Input : Prefix : *+AB-CD Output : Postfix : AB+CD-* Explanation : Prefix to Infix : (A+B) * (C-D) Infix to Postfix : AB+CD-* Input : Prefix : *-A/BC-/AKL Output : Postfix : ABC/-AK/L-* Explanation : Prefix to Infix : A-(B/C)*(A/K)-L Infix to Postfix : ABC/-AK/L-*
Algorithm for Prefix to Postfix:
- Read the Prefix expression in reverse order (from right to left)
- 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 after them.
string = operand1 + operand2 + operator
And push the resultant string back to Stack
- Repeat the above steps until end of Prefix expression.
Postfix : ABC/-AK/L-*
- Postfix to Prefix Conversion
- Prefix to Infix Conversion
- Infix to Prefix conversion using two stacks
- Postfix to Infix
- Stack | Set 2 (Infix to Postfix)
- Stack | Set 4 (Evaluation of Postfix Expression)
- Infix to Postfix using different Precedence Values for In-Stack and Out-Stack
- Decimal to octal conversion with minimum use of arithmetic operators
- Evaluation of Prefix Expressions
- Longest prefix which is also suffix
- Strings from an array which are not prefix of any other string
- Maximum occurrence of prefix in the Array
- Longest Common Prefix using Trie
- Longest Common Prefix using Sorting
- String from prefix and suffix of given two strings
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.