# 110 Balanced Binary Tree

## 110. Balanced Binary Tree

## 1. Question

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 ofeverynode never differ by more than 1.

## 2. Implementation

(1) DFS

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

        return dfs(root) != -1;
    }

    public int dfs(TreeNode node) {
        if (node == null) {
            return 0;
        }

        int leftHeight = dfs(node.left);
        int rightHeight = dfs(node.right);

        if (leftHeight == -1 || rightHeight == -1 || Math.abs(leftHeight - rightHeight) > 1) {
            return -1;
        }
        return Math.max(leftHeight, rightHeight) + 1;
    }
}
```

## 3. Time & Space Complexity

DFS: 时间复杂度: O(n), 空间复杂度: O(h)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://protegejj.gitbook.io/algorithm-practice/leetcode/tree/110-balanced-binary-tree.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.