题解 | #括号生成#

#
# 
# @param n int整型 
# @return string字符串一维数组
#
class Solution:
    def generateParenthesis(self , n ):
        # write code here
        if n==0:
            return []

        result = []
        self.helpler(n, n, '', result)
        return result

    def helpler(self, l, r, item, result):
        if r<l:
            return
        if l==0 and r == 0:
            result.append(item)
        if l>0:
            self.helpler(l-1, r, item +'(', result)
        if r>0:
            self.helpler(l, r-1, item +')', result)