Return a unique list of strings each of length 2*n which have balanced paranthesis

balanced_paranthesis.py

from typing import List

def generate_all_paranthesis(n: int) -> List[str]:
	'Return a unique list of strings each of length 2*n which have balanced paranthesis'
	all_paranthesis = []
	backtrack_helper(all_paranthesis, "", 0, 0, n)
	return all_paranthesis


def backtrack_helper(all_paranthesis: List[str], curr_str: str, open: int, close: int, n: int) -> None:
	"""
	Backtracking helper for generate_all_paranthesis() which builds each string 
	and adds it to the given list when fully built.
	"""
	if len(curr_str) == 2*n:
		all_paranthesis.append(curr_str)
	if open < n: 
		backtrack_helper(all_paranthesis, curr_str + "(", open+1, close, n)
	if close < open:
		backtrack_helper(all_paranthesis, curr_str + ")", open, close+1, n)


assert generate_all_paranthesis(2) == ["(())", "()()"]