class Solution:
    def getMinimumDifference(self, root: TreeNode) -> int:
        self.preVal = None
        self.res = float('inf')
        self.dfs(root)
        return self.res
    def dfs(self,root):
        if not root: return
        self.dfs(root.left)
        if self.preVal != None:
            self.res = min(self.res,root.val-self.preVal)
        self.preVal = root.val
        self.dfs(root.right)

树 简单

https://leetcode-cn.com/problems/minimum-absolute-difference-in-bst/

与 0783.二叉搜索树节点最小距离 相同