Create minimum-distance-between-bst-nodes.py

Author: kamyu104

Python/minimum-distance-between-bst-nodes.py

@@ -0,0 +1,54 @@
+# Time:  O(n)
+# Space: O(h)
+
+# 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:
+# - The size of the BST will be between 2 and 100.
+# - The BST is always valid, each node's value is an integer, and each node's value is different.
+
+# 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
+        """
+        def dfs(node):
+            if not node:
+                return
+            dfs(node.left)
+            self.result = min(self.result, node.val-self.prev)
+            self.prev = node.val
+            dfs(node.right)
+
+        self.prev = float('-inf')
+        self.result = float('inf')
+        dfs(root)
+        return self.result
+