**Objective: **Given a Postfix expression, write an algorithm to convert it into prefix expression.

**Example**:

Input: Postfix expression:A B +Output: Prefix expression-+ A BInput: Postfix expression:ABC/-AK/L-*Output: Infix expression:*-A/BC-/AKL

**Approach**: Use Stack

**Algorithm:**

Iterate the given expression from left to right, one character at a time

- If the character is operand, push it to stack.
- If the character is operator,
- Pop operand from the stack, say it’s s1.
- Pop operand from the stack, say it’s s2.
- perform
**(operator s2 s1)**and push it to stack.

- Once the expression iteration is completed, initialize the result string and pop out from the stack and add it to the result.
- Return the result.

Please walk through the example below for more understanding.

**Java Code:**

**Output:**

Postfix Expression: ABC/-AK/L-* Prefix Expression: *-A/BC-/AKL