783. Minimum Distance Between BST Nodes

https://leetcode.com/problems/minimum-distance-between-bst-nodes

Python

In-Order Travel

from math import inf
from typing import Optional


class Solution:
    def minDiffInBST(self, root: Optional[TreeNode]) -> int:
        result = inf
        pre = None

        def inorder(node: Optional[TreeNode]):
            if not node:
                return

            nonlocal pre
            nonlocal result

            inorder(node.left)
            if pre is not None:
                result = min(result, node.val-pre)

            pre = node.val
            inorder(node.right)

        inorder(root)

        return result