[Leetcode] Validate Binary Search tree (check if it is a two-fork find) Python

Given a binary tree, determine if it is a valid binary search tree (BST).

Assume a BST is defined as follows:

• The left subtree of a node contains only nodes with keys less than the node ' s key.
• The right subtree of a node contains only nodes with keys greater than the node ' s key.
• Both the left and right subtrees must also is binary search trees.

Leetcode has given the definition of a two-fork search tree.

classSolution:#@param root, a tree node    #@return A Boolean    defIsvalidbst (self, root):ifRoot isNone:returnTruereturnSelf.helper (root,-99999,999999)        #Left ~ Right is the value range of node    defHelper (self,root,left,right):ifRoot isNone:returnTrueifRoot.val <= LeftorRoot.val >=Right :#out of range            returnFalsereturnSelf.helper (Root.left,left,root.val) andSelf.helper (Root.right,root.val,right)

After I find the drawing tool, I'll update some of the graphs.

[Leetcode] Validate Binary Search tree (check if it is a two-fork find) Python