Generate Parentheses

Problem:

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

For example, given n = 3, a solution set is:

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

Analysis:
DFS

Solution:

1:  public class Solution {  
2:    public ArrayList<String> generateParenthesis(int n) {  
3:      ArrayList<String> result=new ArrayList<String>();  
4:      DoDSF("",n,n,result);  
5:      return result;  
6:    }  
7:    private void DoDSF(String prefix, int left, int right, ArrayList<String> result)  
8:    {  
9:      if(left==0&& right==0)  
10:      {  
11:        result.add(prefix);  
12:        return;  
13:      }  
14:      if(left!=0)  
15:       DoDSF(prefix+"(",left-1,right,result);  
16:      if(left<right)  
17:        DoDSF(prefix+")",left,right-1,result);  
18:       return;  
19:    }  
20:  }