Remove Outermost Parentheses

Problem

Remove the outermost pair of every primitive group in the balanced parentheses string s and return the concatenation of the inner parts.

Track the current nesting depth: append an opening bracket only when the depth before it is positive, and append a closing bracket only when the depth after it is positive. Assume s is a valid parentheses string.

Hint

A primitive group returns to depth zero exactly at its closing outer bracket.

Test cases

case 1

in: ["(()())(())"]

expected: "()()()"

case 2

in: ["(()())(())(()(()))"]

expected: "()()()()(())"

case 3

in: ["()()"]

expected: ""

case 4

in: ["(()())"]

expected: "()()"

case 5

in: [""]

expected: ""

Starter codePython

def remove_outer_parentheses(s):
    # Your code here
    pass

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