SWEA1231 중위순회 (java)

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
 
 
 
public class Solution {
    public static char[] a;
    public static int N;
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 
        int T = 10;
        for (int tc = 1; tc <= T; tc++) {
            N = Integer.parseInt(br.readLine());
 
            a = new char[N+1];
            for (int i = 0; i < N; i++) {
                StringTokenizer st = new StringTokenizer(br.readLine());
                st.nextToken();
                a[i+1] = st.nextToken().charAt(0);
                while(st.countTokens()!=0)
                    st.nextToken();
            }
            System.out.print("#" + tc + " ");
            inorder(1);
            System.out.println();
        }
         
 
    }
 
    public static void inorder(int i) {
        if (1<=i && i<= N && a[i] != 0) {//a[i] != a[i] != '\u0000'
            //node != null 과 같음
            inorder(2*i);
            System.out.print(a[i]);
            inorder(2*i+1);
        }
    }
 
}