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+## Minimum Distance Between BST Nodes
+
+#### Description
+
+[link](https://leetcode.com/problems/n-ary-tree-postorder-traversal/)
+
+---
+
+#### Solution
+
+- See Code
+
+---
+
+#### Code
+
+> Complexity  T : O(N)   M : O(n)
+
+```python
+# 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:
+        stack = []
+        ans, pre = float("inf"), float("-inf")
+        while root or stack:
+            if root:
+                stack.append(root)
+                root = root.left
+            else:
+                root = stack.pop()
+                ans = min(ans, root.val - pre)
+                pre = root.val
+                root = root.right
+        
+        return ans
+```