Validate Binary Search Tree

Problem:

Given a binary tree, determine if it is a valid binary search tree (BST).

Examples:

Example 1:
   2
   / \
  1   3


Binary tree [2,1,3], return true.
Example 2:
   1
   / \
  2   3


Binary tree [1,2,3], return false.
				

Note:
Assume a BST is defined as follows:

Values in a binary tree will always be STRICTLY greater than 0 and also be less than 100

Hints and Answer Checklist