Postfix Expression Evaluation

Problem

Evaluate an arithmetic expression given in postfix (reverse Polish) notation.

tokens is a list of strings, each either an integer or one of the operators +, -, *, /. For each operator, pop the top two values b then a and push a op b. Division truncates toward zero.

Return the final integer result.

Hint

Operands go on the stack; an operator pops two operands and pushes the result.

Test cases

case 1

in: [["2","1","+","3","*"]]

expected: 9

case 2

in: [["4","13","5","/","+"]]

expected: 6

case 3

in: [["3","4","+","2","*"]]

expected: 14

case 4

in: [["10","6","9","3","+","-11","*","/","*","17","+","5","+"]]

expected: 22

Starter codePython

def eval_postfix(tokens):
    # Your code here
    pass

4 test cases · run your code against them in the editor