Algorithm:-

Suppose Q is an arithmetic expression written in infix notation . this algorithm find equivalent postfix expression P.

- Push “(“onto Stack, and add “)” to the end of Q.
- Scan Q from left to right and repeat Step 3 to 6 for each element of Q until the Stack is empty.
- If an operand is encountered, add it to P.
- If a left parenthesis is encountered, push it onto Stack.
- If an operator is encountered ,then:
- Repeatedly pop from Stack and add to P each operator (on the top of Stack) which has the same precedence as or higher precedence than operator.
- Add operator to Stack.

[End of If]

- If a right parenthesis is encountered ,then:
- Repeatedly pop from Stack and add to P each operator (on the top of Stack) until a left parenthesis is encountered.
- Remove the left Parenthesis