Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as:

a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Example 1:

Given the following tree [3,9,20,null,null,15,7]:

    3
   / \
  9  20
    /  \
   15   7

Return true.

Example 2:

Given the following tree [1,2,2,3,3,null,null,4,4]:

       1
      / \
     2   2
    / \
   3   3
  / \
 4   4

Return false.

 public boolean isBalanced(TreeNode root) {
        if(root==null)
            return true;
        return Math.abs(deep(root.left)-deep(root.right))<=1 && isBalanced(root.left) && isBalanced(root.right);
        //左子樹和右子樹的高度差為1  且 左子樹是平衡二乘樹   右子樹是平衡二叉樹
    }
    public int  deep(TreeNode node)//求樹高程式碼
    {
        if(node==null)
            return 0;
        return Math.max(deep(node.left),deep(node.right))+1;       
        
    }