> For the complete documentation index, see [llms.txt](https://ondrej-kvasnovsky-2.gitbook.io/algorithms/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ondrej-kvasnovsky-2.gitbook.io/algorithms/data-structures/binary-tree/balanced-binary-tree.md).

# Balanced Binary Tree

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.

## Solution

```
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    private boolean balanced = true;

    public boolean isBalanced(TreeNode root) {
        depth(root);
        return balanced;
    }

    private int depth(TreeNode node) {
        if (node == null) return 0;
        int left = depth(node.left);
        int right = depth(node.right);
        if (Math.abs(left - right) > 1) {
            balanced = false;
        }
        return Math.max(left, right) + 1;
    }
}
```


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