783. Minimum Distance Between BST Nodes BST节点之间的最小距离

Given a Binary Search Tree (BST) with the root node root, return the minimum difference between the values of any two different nodes in the tree.

Example :

Input: root = [4,2,6,1,3,null,null]
Output: 1
Explanation:
Note that root is a TreeNode object, not an array.

The given tree [4,2,6,1,3,null,null] is represented by the following diagram:

          4
        /   
      2      6
     /     
    1   3  

while the minimum difference in this tree is 1, it occurs between node 1 and node 2, also between node 3 and node 2.

Note:

1. The size of the BST will be between 2 and 100.
2. The BST is always valid, each node's value is an integer, and each node's value is different.

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# 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):         """         :type root: TreeNode         :rtype: int         """         res = float('inf')         pre = -float('inf')           def find(root):             nonlocal res             nonlocal pre             if root.left:                 find(root.left)             res = min(res, root.val - pre)             pre = root.val             if root.right:                 find(root.right)           find(root)         return res

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