Did the pre-order traversal problem

1008/main.py

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+class TreeNode:
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+    def __str__(self):
+        return "\nValue: " + str(self.val) + "\nLeft:" + str(self.left) + "\nRight:" + str(self.right)
+
+class Solution:
+    def bstFromPreorder(self, preorder):
+        
+        if preorder is None or len(preorder) == 0:
+            return None
+        elif len(preorder) == 1:
+            return TreeNode(preorder[0])
+        
+        root = TreeNode(preorder[0])
+        
+        # now collect the nodes that are less than root and make a tree from them
+        leftChildrenItems = list(filter(lambda x: x < preorder[0], preorder[1:]))
+        rightChildrenItems = list(filter(lambda x: x > preorder[0], preorder[1:])) # don't need >= because items are distinct
+            
+        root.left = self.bstFromPreorder(leftChildrenItems)
+        root.right = self.bstFromPreorder(rightChildrenItems) 
+        
+        return root        
+
+s = Solution()
+print("Expected: [4, 2]")
+print("Got:", s.bstFromPreorder([4, 2]))

1008/problem.txt

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+Return the root node of a binary search tree that matches the given preorder traversal.
+
+(Recall that a binary search tree is a binary tree where for every node, any descendant of node.left has a value < node.val, and any descendant of node.right has a value > node.val.  Also recall that a preorder traversal displays the value of the node first, then traverses node.left, then traverses node.right.)
+
+Example 1:
+
+Input: [8,5,1,7,10,12]
+Output: [8,5,10,1,7,null,12]
+
+Note: 
+
+    1 <= preorder.length <= 100
+    The values of preorder are distinct.

1008/run.sh

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+#!/bin/bash
+
+python3 main.py