22. Generate Parentheses - Leetcode

solution.py

# https://leetcode.com/problems/generate-parentheses/#/description
class Solution(object):
    def generateParenthesis(self, n):
        """
        :type n: int
        :rtype: List[str]
        """
        return(self.createParentheses("", n, n))
    
    def createParentheses(self, string, num_open, num_closed):
        if num_open == num_closed == 0:
            return [string]

        answer_strings = []
        if num_open == num_closed:
            for s in self.createParentheses(string + "(", num_open - 1, num_closed):
                answer_strings.append(s)
        elif num_open > 0 and num_open < num_closed:
            for s in self.createParentheses(string + "(", num_open - 1, num_closed):
                answer_strings.append(s)
            for s in self.createParentheses(string + ")", num_open, num_closed - 1):
                answer_strings.append(s)
        elif num_open == 0:
            for s in self.createParentheses(string + ")", num_open, num_closed - 1):
                answer_strings.append(s)
        return answer_strings

I found that solution very popular and helpful:
https://www.youtube.com/watch?v=N3O1snRqacI&ab_channel=EricProgramming