Perfect_Binary_Tree.java

// { Driver Code Starts
//Initial Template for Java

import java.io.*;
import java.util.*;
import java.lang.*;

class Node {
  int data;
  Node left, right;

  public Node(int data) {
    this.data = data;
  }
}

class GFG {

  static Node buildTree(String str) {

    if (str.length() == 0 || str.charAt(0) == 'N') {
      return null;
    }

    String ip[] = str.split(" ");
    // Create the root of the tree
    Node root = new Node(Integer.parseInt(ip[0]));
    // Push the root to the queue

    Queue<Node> queue = new LinkedList<>();

    queue.add(root);
    // Starting from the second element

    int i = 1;
    while (queue.size() > 0 && i < ip.length) {

      // Get and remove the front of the queue
      Node currNode = queue.peek();
      queue.remove();

      // Get the current node's value from the string
      String currVal = ip[i];

      // If the left child is not null
      if (!currVal.equals("N")) {

        // Create the left child for the current node
        currNode.left = new Node(Integer.parseInt(currVal));
        // Push it to the queue
        queue.add(currNode.left);
      }

      // For the right child
      i++;
      if (i >= ip.length)
        break;

      currVal = ip[i];

      // If the right child is not null
      if (!currVal.equals("N")) {

        // Create the right child for the current node
        currNode.right = new Node(Integer.parseInt(currVal));

        // Push it to the queue
        queue.add(currNode.right);
      }
      i++;
    }

    return root;
  }

  public static void inorder(Node root) {
    if (root == null)
      return;

    inorder(root.left);
    System.out.print(root.data + " ");
    inorder(root.right);
  }

  public static void main(String[] args) throws IOException {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    int t = Integer.parseInt(br.readLine());
    while (t-- > 0) {
      String s = br.readLine();
      Node root = buildTree(s);
      Solution obj = new Solution();
      boolean res = obj.isPerfect(root);
      if (res) {
        System.out.println("YES");
      } else {
        System.out.println("NO");
      }
    }
  }
}

class Solution {
  public boolean isPerfect(Node root) {
    if (root == null)
      return true;
    int lh = height(root.left);
    int rh = height(root.right);
    return Math.abs(lh - rh) == 0 && isPerfect(root.left) && isPerfect(root.right);
  }

  public int height(Node root) {
    if (root == null) {
      return 0;
    }

    return Math.max(height(root.left), height(root.right)) + 1;
  }
}