FunWithTreesIsPerfect.java

import java.util.*;

public class TreeNode {

    TreeNode left;
    TreeNode right;

    public static boolean isPerfect(TreeNode root) {
        if(root == null){
         return true;
        }
        Queue queue = new LinkedList<TreeNode>();
        queue.add(root);
        int treeSize = 0;        
        while (!queue.isEmpty()){
            TreeNode leafIterative = (TreeNode)queue.remove();
            treeSize++;
            if(leafIterative.left != null){
                queue.add(leafIterative.left);
            }
            if(leafIterative.right != null){
                queue.add(leafIterative.right);
            }
        }
        return isPerfect(treeSize);
    }
    
    static boolean isPerfect(int size){
      boolean result = false;
      int index = 0;
      double expectedSize = 0;
      while(!result && expectedSize< size){
        expectedSize += Math.pow(2,index);
        if((double)size == expectedSize){
          result = true;
        }
        index++;
      }
      return result;    
    }
    
    static TreeNode leaf() {
        return new TreeNode();
    }

    static TreeNode join(TreeNode left, TreeNode right) {
        return new TreeNode().withChildren(left, right);
    }

    TreeNode withLeft(TreeNode left) {
        this.left = left;
        return this;
    }

    TreeNode withRight(TreeNode right) {
        this.right = right;
        return this;
    }

    TreeNode withChildren(TreeNode left, TreeNode right) {
        this.left = left;
        this.right = right;
        return this;
    }

    TreeNode withLeftLeaf() {
        return withLeft(leaf());
    }

    TreeNode withRightLeaf() {
        return withRight(leaf());
    }

    TreeNode withLeaves() {
        return withChildren(leaf(), leaf());
    }
}