Learn How To Convert Postfix To Prefix Notation using Stack in C Programming Language. Before you proceed further with this code, you must know the complete operations of **stack data structure**.

The Postfix notation is also known as **Reverse Polish Notation** and the Prefix notation is also known as **Polish Notation**.

#### Postfix To Prefix Conversion Example

**Postfix String: 44+**

**Prefix String: +44**

#### Algorithm To Convert Postfix Expression into Prefix Notation

- Scan the Postfix Expression from Left To Right.
- If the character is an Operand, then Push it on to the Stack.
- If the character is an Operator, then Pop Operand 1 and Operand 2 and concatenate them and Push the result on the Stack.
- Repeat the above steps until the Postfix Expression is scanned completely.
- To get the Prefix Expression, Pop the remaining elements of the Stack.

#### C Program For Postfix To Prefix Conversion using Stack Data Structure

#include<string.h> #include<stdio.h> #include<stdlib.h> #define MAX 20 char str[MAX], stack[MAX]; int top = -1; char pop() { return stack[top--]; } void push(char ch) { stack[++top] = ch; } void postfix_to_prefix(char expression[]) { int count, length; length = strlen(expression); printf("\nPrefix Expression:\t"); for(count = length - 1; count >= 0; count--) { printf("%c", expression[count]); } } int main() { char postfix_expression[35]; printf("\nEnter Postfix Expression:\t"); scanf("%s", postfix_expression); postfix_to_prefix(postfix_expression); printf("\n"); return 0; }

#### Output

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You are an idiot