# Introduction A binary search tree (BST) is a tree data structure in which each node has at most two children, which are referred to as the left child and the right child. A valid BST is a tree in which all the nodes in the left subtree of a node have a value less than the node's value, and all the nodes in the right subtree have a value greater than the node's value. In this challenge, we will determine if a given tree is a valid binary search tree.

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