Given the root of a binary tree, determine if it is a valid binary search tree (BST). A valid BST has these properties: - The left subtree of a node contains only nodes with keys less than the node's key - The right subtree contains only nodes with keys greater than the node's key - Both left and right subtrees must also be valid BSTs Example: [2, 1, 3] is valid. [5, 1, 4, null, null, 3, 6] is not (the 4 is in the right subtree of 5 but 3 < 5).
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$ curl repovive.com/roadmaps/maang-interview-prep/trees-bst/problem-validate-binary-search-tree
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