53-2.py

import sys


# Definition for a binary tree node.
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None


class Solution:
    def minDiffInBST(self, root: TreeNode) -> int:
        prev = -sys.maxsize
        result = sys.maxsize

        stack = []
        node = root

        # 반복 구조 중위 순회 비교 결과
        while stack or node:
            while node:
                stack.append(node)
                node = node.left

            node = stack.pop()

            result = min(result, node.val - prev)
            prev = node.val

            node = node.right

        return result