private boolean isBalanced = true;

public boolean IsBalanced_Solution(TreeNode root) {
    height(root);
    return isBalanced;
}

private int height(TreeNode root) {
    if (root == null)
        return 0;
    int left = height(root.left);
    int right = height(root.right);
    if (Math.abs(left - right) > 1)
        isBalanced = false;
    return 1 + Math.max(left, right);
}