09 Sept 2026•Easy•Go / Python / TypeScript

Remove Outermost Parentheses

Remove the first and last parenthesis from every primitive part of a valid parentheses string.

Track nesting depth, appending an opening parenthesis only after entering a primitive and a closing one only before leaving it.

Complexity

O(n) time and O(n) output space.

Solution files

Go•remove-outermost-parentheses/solution.go

package main

func removeOuterParentheses(s string) string {
	result := make([]byte, 0, len(s))
	depth := 0
	for index := range s {
		if s[index] == '(' {
			if depth > 0 {
				result = append(result, s[index])
			}
			depth++
		} else {
			depth--
			if depth > 0 {
				result = append(result, s[index])
			}
		}
	}
	return string(result)
}

Python•remove-outermost-parentheses/solution.py

class Solution:
    def removeOuterParentheses(self, s: str) -> str:
        result: list[str] = []; depth = 0
        for character in s:
            if character == "(":
                if depth: result.append(character)
                depth += 1
            else:
                depth -= 1
                if depth: result.append(character)
        return "".join(result)

TypeScript•remove-outermost-parentheses/solution.ts

function removeOuterParentheses(s: string): string {
  const result: string[] = []; let depth = 0;
  for (const character of s) { if (character === "(") { if (depth > 0) result.push(character); depth += 1; } else { depth -= 1; if (depth > 0) result.push(character); } }
  return result.join("");
}