Write a C Program to convert infix to postfix and evaluate postfix expression. Here’s simple Program to convert infix to postfix and evaluate postfix expression in C Programming Language.

#gatecse #cprogramming #expressionevaluaiton #infix #postfix #appliedgate #gate2022Subject Name: C-ProgrammingChapter Name: Expression EvaluationTopic Name. Algorithm to Convert Infix to Postfix Expression Using Stack. Following is the algorithm to convert infix expression into Reverse Polish notation. Initialize the Stack. Scan the operator from left to right in the infix expression. If the leftmost character is an operand, set it as the current output to the Postfix string.

What is Stack ?

Stack is an abstract data type with a bounded(predefined) capacity. It is a simple data structure that allows adding and removing elements in a particular order. Every time an element is added, it goes on the top of the stack, the only element that can be removed is the element that was at the top of the stack, just like a pile of objects.

Given an infix expression, convert it to the postfix expression. Assume that the infix expression is a string of tokens without any spaces. For example, Input: A×B+C. Input: (A+B)× (C/D) Output: AB+CD/×. Input: A× (B×C+D×E)+F. Output: ABC×DE×+×F+. C program to convert: 1.Postfix to Infix 2.Postfix to Prefix. Infix to Postfix Conversion Examples. Since the step-by-step infix to postfix examples are quite long, I will first provide a simple example without any parentheses, and then provide a more complex example that includes parentheses and a case of right-to-left associativity. Both examples were generated by the infix to postfix calculator on this.

Basic Operations : :

push() − Pushing (storing) an element on the stack.

pop() − Removing (accessing) an element from the stack.

peek() − get the top data element of the stack, without removing it.

isFull() − check if stack is full.

C++ Infix To Postfix Algorithm

isEmpty() − check if stack is empty.

Below is the source code for C Program to convert infix to postfix and evaluate postfix expression which is successfully compiled and run on Windows System to produce desired output as shown below : https://cleverjoomla.amebaownd.com/posts/19095462.

SOURCE CODE : :

OUTPUT : :

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Stack is a data structure used for storing collection of data where order in which data is arriving is important. In Stack, insertion and deletion both happened from the same end which is known as “Top”.
The data which is arrived last will be deleted first in Stack. This data ordering is called as Last in First out or LIFO. Before going ahead have a look into Stack basics and Generic Stack Implementation.

Let’s have a look on basic class definition for Generic Stack.

Infix Notation

This is the most common notation which we use generally in out writings. In this notation, mathematical operators (such as +, -, * etc.) are written in-between there operands. eg:
A+B,
(A*B)+C

Postfix Notation

In this notation, operators are written after there operands. eg:
AB+
AB*C+

For more information related to Expression notation check Prefix, Postfix and Infix Expression notations.

Infix to Postfix conversion

Here we are going to define the algorithm to convert an Infix expression notation to Postfix expression notation.

Converting Infix To Postfix

Algorithm to convert Infix to Postfix

Define a Stack
For each character ‘a’ in Infix Expression
- if character is operands then put it in output expression
- if character is an right parenthesis ‘)’, then pop all the items from stack and put it in output expression till left parenthesis ‘(‘ is encountered
- if character is an operator ‘b’ or left parenthesis then
  - pop all tokens from the stack and put it into the output expression until one of the higher priority operator or left parenthesis is encountered.
  - push b into the stack.

Let’s look into an example to make it more clear.
In below example we will apply above algorithm to convert infix expression “(A+B)*C+(D+E)” into Postfix expression.

Few of the functions used below are explained in Generic Stack Implementation. Refer those before going ahead.
Let’s look into the sample code.

Let’s define a main function to use above methods.

Lua And C Infix To Postfix

Let’s analyze the output of this main function.