Check if a given array can represent Preorder Traversal of Binary Search Tree

Given an array of numbers, return true if given array can represent preorder traversal of a Binary Search Tree, else return false. Expected time complexity is O(n).

Input:  pre[] = {2, 4, 3}
Output: true
    2
     \
      4
     /
    3
Input:  pre[] = {2, 4, 1}
Output: false
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