Given an array of integers in[] representing inorder traversal of elements of a binary tree. Return true if the given inorder traversal can be of a valid Binary Search Tree.
Note - All the keys in BST must be unique

Example 1:
Input: in = [8, 14, 45, 64, 100]
Output: True
Example 2:
Input: in[] = [5, 6, 1, 8, 7]
Output: False

Your Task:
Complete the function isBSTTraversal() which takes an integer array in[] as input and return true if the traversal represents a BST.

Expected Time Complexity: O(n)
Expected Space Complexity: O(1)

Constraints:
1<=n<=10^{5}
1<=in[i]<=10^{9}

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