# LeetCode 235: Lowest Common Ancestor Of A Binary Search Tree — Step-by-Step Visual Trace

**Medium** — Binary Search Tree | Tree | Recursion

## The Problem

Find the lowest common ancestor (LCA) of two given nodes in a binary search tree, where the LCA is the deepest node that has both nodes as descendants.

## Approach

Leverage the BST property to recursively navigate the tree. If both nodes are smaller than current node, go left; if both are larger, go right; otherwise the current node is the LCA.

**Time:** O(h) · **Space:** O(h)

## Code

```python
class Solution:
    def lowestCommonAncestor(
        self, root: TreeNode, p: TreeNode, q: TreeNode
    ) -> TreeNode:
        if root.val > p.val and root.val > q.val:
            return self.lowestCommonAncestor(root.left, p, q)
        elif root.val < p.val and root.val < q.val:
            return self.lowestCommonAncestor(root.right, p, q)
        else:
            return root
```

## Watch It Run

> **[Open interactive visualization](https://tracelit.dev/app?trace=0235_lowest-common-ancestor-of-a-binary-search-tree)**

> **Try it yourself:** Open [TraceLit](https://tracelit.dev/app?trace=0235_lowest-common-ancestor-of-a-binary-search-tree) and step through every line.

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