Validate Binary Search Tree | Problems

Given the root of a binary tree, determine if it is a valid BST.

Example: root = [2,1,3] → true, root = [5,1,4,null,null,3,6] → false

Sample Input

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Sample Output

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Constraints

1 <= number of nodes <= 10^4
-2^31 <= Node.val <= 2^31 - 1

Topics

Tree Binary Tree DFS

DFS with Range

function isValidBST(root) {
  function validate(node, min, max) {
    if (!node) return true;
    if (node.val <= min || node.val >= max) return false;
    return validate(node.left, min, node.val) && validate(node.right, node.val, max);
  }
  return validate(root, -Infinity, Infinity);
}

Time: O(n) | Space: O(h)

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