题解 | #括号生成#

class Solution:
    def generateParenthesis(self , n: int) -> List[str]:
        # write code here
        s = '('*n + ')'*n

        rst = {}

        def dfs(l, r, s):
            if l == n and r == n:
                if s not in rst:
                    rst[s] = 1
                return

            if l <= n:
                dfs(l + 1, r, s + '(')
            
            if r <= n  and l > r:
                dfs(l, r+1, s + ')')

        dfs(0, 0, '')
        return list(rst.keys())

搞清楚dfs的方向