# leetle

## 38. Balanced Binary Tree

Write a function `solve` that checks if a binary tree is height-balanced. A height-balanced binary tree is defined as a binary tree in which the left and right subtrees of every node differ in height by no more than 1.

**Example:** `Input: [3,9,20,None,None,15,7]` `Output: True`

Make sure you `return` your solution, don't print!

### Python3

```python
def solve(root):
    pass
```

# Binary Tree Definition

```python
class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right
```