## 题目描述：

LeetCode 783. Minimum Distance Between BST Nodes

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.

## Python代码：

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

class Solution(object):
def minDiffInBST(self, root):
"""
:type root: TreeNode
:rtype: int
"""
ans = 0x7FFFFFFF
if root.left:
lmax = root.left
while lmax.right: lmax = lmax.right
ans = min(ans, root.val - lmax.val)
ans = min(ans, self.minDiffInBST(root.left))
if root.right:
rmin = root.right
while rmin.left: rmin = rmin.left
ans = min(ans, rmin.val - root.val)
ans = min(ans, self.minDiffInBST(root.right))
return ans
``````

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