Leetcode 22. 括号生成 (括号匹配，dfs）

输入：n = 3
输出：[
       "((()))",
       "(()())",
       "(())()",
       "()(())",
       "()()()"
     ]

class Solution {
    List<String> ans=new ArrayList<>();
    public List<String> generateParenthesis(int n) {
        dfs(n,n,"");
        return ans;

    }
    public void dfs(int left,int right,String tep)
    {
        //System.out.println(left+" "+right);
        if(left==0&&right==0)
        {
            ans.add(tep);
            return ;
        }
        if(left>0)dfs(left-1,right,tep+"(");
        if(right>left)dfs(left,right-1,tep+")");
    }
}