GenerateParenthesis

// Driver code
import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter number: "); // enter input in range 1 to 8
        int input = sc.nextInt();
        Solution obj = new Solution();
        ArrayList<String> ans = obj.generateParenthesis(input);
        System.out.print(ans);
    }
}
// if open less than n add open
// if closed less than open add closed
// if open equals closed add string and return 
class Solution {
    ArrayList<String> al;
    
    public void recur(int n, int open, int closed, StringBuilder s){
        if(open == n && closed == n){
            String ans = s.toString();
            al.add(ans);
            return;
        }
        if(open < n){
            s.append('(');
            recur(n,open+1,closed,s);
             s.delete(s.length() - 1, s.length());
        }
        if(closed < open){
            s.append(')');
            recur(n,open,closed+1,s);
            s.delete(s.length() - 1, s.length());
        }
    }
    public ArrayList<String> generateParenthesis(int n) {
        al = new ArrayList<>();
        StringBuilder s = new StringBuilder();
        recur(n,0,0,s);
        return al;
    }
}