# LeetCode 110: Balanced Binary Tree — Step-by-Step Visual Trace

**Easy** — Binary Tree | Recursion | Tree Traversal | Depth-First Search

## The Problem

Determine if a binary tree is height-balanced, where for every node the heights of its left and right subtrees differ by at most one.

## Approach

Use a recursive helper function to calculate height while simultaneously checking balance conditions. If any subtree is unbalanced, propagate infinity upward to indicate imbalance, otherwise return the actual height.

**Time:** O(n) · **Space:** O(h)

## Code

```python
class Solution:
    def isBalanced(self, root: TreeNode) -> bool:
        def height(node):
            if not node:
                return 0
            left_height = height(node.left)
            right_height = height(node.right)
            if abs(left_height - right_height) > 1:
                return float("inf")  # Indicate imbalance
            return max(left_height, right_height) + 1

        return height(root) != float("inf")
```

## Watch It Run

> **[Open interactive visualization](https://tracelit.dev/app?trace=0110_balanced-binary-tree)**

> **Try it yourself:** Open [TraceLit](https://tracelit.dev/app?trace=0110_balanced-binary-tree) and step through every line.

---

*Built with [TraceLit](https://tracelit.dev) — the visual algorithm tracer for LeetCode practice.*