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:

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

 

solution:DFS模版

package leetcode2;import java.util.ArrayList;public class Generate_parenthese {    public static ArrayList
     
       generateParenthesis(int n) {        ArrayList
      
        reArrayList=new ArrayList
       
        ();        String s=new String();        dfs(reArrayList,s,n,n); //DFS的模版递归 dfs(list
        
         ,E,deep,somethingConstant)        return reArrayList;    }   public static void dfs(ArrayList
         
           reArrayList, String s, int left,int right) {        // TODO Auto-generated method stub        // 先考虑deep极值,此处为left，right个数,直接return       if(right
          
           0){ dfs(reArrayList, s+'(', left-1, right); } if(right>0){ dfs(reArrayList, s+')', left, right-1); } } public static void main(String[] args) { // TODO Auto-generated method stub System.out.println(generateParenthesis(3)); }}