生成括号

给定 n 对括号，请写一个函数以将其生成新的括号组合，并返回所有组合结果。

样例

给定 n = 3, 可生成的组合如下:

"((()))", "(()())", "(())()", "()(())", "()()()"

 

public class Solution {
    /**
     * @param n n pairs
     * @return All combinations of well-formed parentheses
     */
    public ArrayList<String> generateParenthesis(int n)
    {
        ArrayList<String> ss = new ArrayList<String>();
        ss = print(n, n, ss, 0);
        return ss;
    }

    ArrayList<String> print(int i, int j, ArrayList<String> ss, int p)
    {
        if (ss.size() == 0)
        {
            String s = "(";
            ss.add(s);
            i--;
        } else
        {
            ArrayList<String> list = new ArrayList();
            if (p == 0)
            {
                for (String s : ss)
                {
                    String s1 = s + "(";
                    list.add(s1);
                }
                i--;
            } else
            {
                for (String s : ss)
                {
                    String s1 = s + ")";
                    list.add(s1);
                }
                j--;
            }
            ss = list;
        }

        ArrayList<String> list = new ArrayList();
        if (i > 0)
        {
            list.addAll(print(i, j, ss, 0));
        }
        if (i < j && j > 0)
        {
            list.addAll(print(i, j, ss, 1));
        }
        if (list.size() == 0)
        {
            return ss;
        }
        return list;
    }
}