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-*
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
- Postfix to Prefix 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++
- Decimal to octal conversion with minimum use of arithmetic operators
- Longest Common Prefix using Word by Word Matching
- Longest Common Prefix using Character by Character Matching
- Longest Common Prefix using Divide and Conquer Algorithm
- Longest Common Prefix using Binary Search
- Longest Common Prefix using Trie
- Longest Common Prefix using Sorting
- Find shortest unique prefix for every word in a given list | Set 2 (Using Sorting)
- Longest palindromic string formed by concatenation of prefix and suffix of a string
- Find minimum shift for longest common prefix
- Convert Infix To Prefix Notation
- Evaluation of Prefix Expressions
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.