To check if a binary tree is a valid BST, you need to ensure that for every node, all values in its left subtree are smaller and all values in its right subtree are larger.

Validating whether a binary tree is a binary search tree (BST) involves checking that the tree satisfies the BST property for every node. Specifically, the value of each node must be greater than all values in its left subtree and less than all values in its right subtree. In TypeScript, this can be done recursively by passing down minimum and maximum constraints. At each node, you check whether its value falls within the allowed range and recursively validate its left and right children. If any node violates the BST property, the tree is not a valid BST. This validation process has a time complexity of O(n), where n is the number of nodes in the tree. Understanding how to validate a BST is important for problems involving tree manipulations, data storage, and search operations in programming.