Basic Calculator with Parentheses

Problem

Evaluate an expression string with non-negative integers, +, -, parentheses and spaces, where a minus sign may also precede an opening parenthesis or a number.

Use a stack to save the result and sign whenever an opening parenthesis appears, restart the running result inside, and fold it back in when the parenthesis closes. The input is always a valid expression.

Hint

Saving both the result and the sign before a parenthesis is what makes nested groups work.

Test cases

case 1

in: ["1 + 1"]

expected: 2

case 2

in: [" 2-1 + 2 "]

expected: 3

case 3

in: ["(1+(4+5+2)-3)+(6+8)"]

expected: 23

case 4

in: ["2-(5-6)"]

expected: 3

case 5

in: ["-(2+3)"]

expected: -5

Starter codePython

def basic_calculator_with_parens(s):
    # Your code here
    pass

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