View difference between Paste ID: ZnTbjyGS and rVQMSvfL

 import java.io.*;
 import java.util.*;
 
 public class BinaryTreeTraversal {
 
     /**
      * @param args
      */
     public static void main(String[] args) {
         Scanner input = new Scanner("input.txt");
         int n = input.nextInt();
         int m = (int) Math.pow(2,n)-1;
-        BinaryNode<Character>[] array = new BinaryNode<Character>[m];
+        List<BinaryNode<Character>> list = new ArrayList<BinaryNode<Character>>(m);
 
         for (Character c : input.nextLine().toCharArray()) {
-            array[i] = new BinaryNode<Character>(Character.isLetter(c) ? c : null);
+            list.add(new BinaryNode<Character>(Character.isLetter(c) ? c : null));
         }
-        BinaryNode<Character> root = array[0];
+        BinaryNode<Character> root = list.get(0);
 
         // HERE: turn the flat, unrelated array of BinaryNode's into a real tree starting with root.
 
         System.out.println(root.toStringPreOrder());
         System.out.println(root.toStringInOrder());
         System.out.println(root.toStringPostOrder());
         // done!
     }
 }