BalancedBinaryTree.java

public class BalancedBinaryTree {

 public static boolean isBalanced(TreeNode root) {
 if(root == null) return true;

 return Math.abs(level(root.left) - level(root.right)) < 1 && isBalanced(root.left) && isBalanced(root.right);
 }

 public static int level(TreeNode node) {
 if(node == null) return 0;
 return Math.max(level(node.left), level(node.right)) + 1;
 }

 public static void main(String[] args) {
 TreeNode node1 = new TreeNode(1);
 TreeNode node2 = new TreeNode(2);
 TreeNode node3 = new TreeNode(3);
 TreeNode node4 = new TreeNode(4);
 TreeNode node5 = new TreeNode(5);
 TreeNode node6 = new TreeNode(6);
 TreeNode node7 = new TreeNode(7);

 node1.left = node2;
 node1.right = node3;
 node2.left = node4;
 node2.right = node5;
 node4.left = node6;
 node4.right = node7;
 System.out.println(isBalanced(node1));
 }
}