数据结构算法操作试题(C++/Python)——括号生成

class Solution(object):
    def generateParenthesis(self, n):
        """
        :type n: int
        :rtype: List[str]
        """
        resList = set()
        if n == 1: return ["()"]
        else:
            for i in self.generateParenthesis(n - 1):
                findParenthesisList = self.find_all(i, '()')
                for j in findParenthesisList:
                    tmpParenth = i[:j+1] + "()" + i[j+1:]
                    resList.add(tmpParenth)
                    tmpParenth = i[:j+2] + "()" + i[j+2:]
                    resList.add(tmpParenth)           
            return list(resList)
            
    def find_all(self, a_str, sub):
        start = 0
        while True:
            start = a_str.find(sub, start)
            if start == -1: return
            yield start
            start += len(sub)