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

        if(Math.abs(treeDepth(root.left) - treeDepth(root.right)) > 1) return false;

        return isBalanced(root.left) && isBalanced(root.right);

    }
    private int treeDepth(TreeNode root){
        if(root == null) return 0;

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