diff --git a/apps/docs/content/(tree)/235-lowest-common-ancestor-of-a-binary-search-tree.mdx b/apps/docs/content/(tree)/235-lowest-common-ancestor-of-a-binary-search-tree.mdx new file mode 100644 index 0000000..97cb5d0 --- /dev/null +++ b/apps/docs/content/(tree)/235-lowest-common-ancestor-of-a-binary-search-tree.mdx @@ -0,0 +1,56 @@ +--- +title: '235. Lowest Common Ancestor of a Binary Search Tree' +description: Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in the BST +sidebar: + label: 'Lowest Common Ancestor of a Binary Search Tree' + badge: 'Medium' +--- + +Binary Search Tree + +### Example 1: +- Input: `root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 8` +- Output: `6` +- Explanation: The LCA of nodes `2` and `8` is `6`. + +### Example 2: +- Input: `root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 4` +- Output: `2` +- Explanation: The LCA of nodes `2` and `4` is `2`, since a node can be a descendant of itself according to the LCA definition. + +### Example 3: +- Input: `root = [2,1], p = 2, q = 1` +- Output: `2` + +### Constraints: + +- The number of nodes in the tree is in the range [2, 10^5]. +- `-10^9 <= Node.val <= 10^9` +- All Node.val are unique. +- `p != q` +- p and q will exist in the BST. + +## Solution + +```py +# Definition for a binary tree node. +# class TreeNode: +# def __init__(self, x): +# self.val = x +# self.left = None +# self.right = None + + +class Solution: + def lowestCommonAncestor( + self, root: "TreeNode", p: "TreeNode", q: "TreeNode" + ) -> "TreeNode": + cur = root + while cur: + if p.val < cur.val and q.val < cur.val: + cur = cur.left + elif p.val > cur.val and q.val > cur.val: + cur = cur.right + else: + return cur +```