DIY: Validate the Binary Search Tree

Solve the interview question "Validate the Binary Search Tree" in this lesson.

Problem statement

For this challenge, you are given an integer array. You have to implement the in_orderBST() function to validate whether the given integer array represents the in-order traversal of a valid binary search tree


  • Nodes count of the binary search tree in the range [1, 10410^4].
  • 231-2^{31} <= Node.value <= 2312^{31} - 1


The input of the in_orderBST() function is an integer array and its length. The following is an example input:



The following is the output of the in_orderBST() function, in case it fulfills the condition:

Valid BST

Otherwise, it outputs the following:

Not valid BST

Coding exercise

Implement the in_orderBST(array,n) function, where array is an integer array that represents the in-order traversal of a binary search tree, and n is the given array’s length.

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