While we use infix expressions in our day to day lives. Computers have trouble understanding this format because they need to keep in mind rules of operator precedence and also brackets. Prefix and Postfix expressions are easier for a computer to understand and evaluate.
Given two operands and and an operator , the infix notation implies that O will be placed in between a and b i.e . When the operator is placed after both operands i.e , it is called postfix notation. And when the operator is placed before the operands i.e , the expression in prefix notation.
Given any infix expression we can obtain the equivalent prefix and postfix format.
Input : A * B + C / D Output : + * A B/ C D Input : (A - B/C) * (A/K-L) Output : *-A/BC-/AKL
To convert an infix to postfix expression refer to this article Stack | Set 2 (Infix to Postfix). We use the same to convert Infix to Prefix.
- Step 1: Reverse the infix expression i.e A+B*C will become C*B+A. Note while reversing each ‘(‘ will become ‘)’ and each ‘)’ becomes ‘(‘.
- Step 2: Obtain the postfix expression of the modified expression i.e CB*A+.
- Step 3: Reverse the postfix expression. Hence in our example prefix is +A*BC.
Below is the C++ implementation of the algorithm.
Stack operations like push() and pop() are performed in constant time. Since we scan all the characters in the expression once the complexity is linear in time i.e .
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- Program to convert Infix notation to Expression Tree
- Infix to Prefix conversion using two stacks
- Prefix to Infix Conversion
- Postfix to Infix
- Infix to Postfix using different Precedence Values for In-Stack and Out-Stack
- Stack | Set 2 (Infix to Postfix)
- Print all words matching a pattern in CamelCase Notation Dictonary
- 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
- Evaluation of Prefix Expressions
- Longest Common Prefix using Linked List
- Longest Common Prefix Matching | Set-6
- Check if suffix and prefix of a string are palindromes
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