题解 | 括号生成

import java.util.*;


public class Solution {

    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param n int整型
     * @return string字符串ArrayList
     */
    public ArrayList<String> generateParenthesis (int n)

    {
       
       ArrayList result = new ArrayList<String>();

       recursionPar(n,result,0,0,"");

       return result;
    }

    public void recursionPar(int n,ArrayList<String> list,int left,int right,String temp){

        if(right == n){
          list.add(new String(temp));
        }

        if(left < n){
            recursionPar(n,list,left+1,right,temp+"(");
        }

        if(right < left){
            recursionPar(n,list,left,right+1,temp+")");
        }
    }

}