# Size of Largest BST in Binary Tree

Easy
0/40
Average time to solve is 10m
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## Problem statement

You have been given a Binary Tree of 'N' nodes, where the nodes have integer values. Your task is to return the size of the largest subtree of the binary tree which is also a BST.

A binary search tree (BST) is a binary tree data structure which has the following properties.

• The left subtree of a node contains only nodes with data less than the node’s data.
• The right subtree of a node contains only nodes with data greater than the node’s data.
• Both the left and right subtrees must also be binary search trees.

Example:
Given binary tree:

In the given binary tree, subtree rooted at 2 is a BST and its size is 3.
Detailed explanation ( Input/output format, Notes, Images )
##### Sample Input 1 :
2 1 3 -1 -1 -1 -1
3

#### Explanation for Sample 1:

In the given binary tree, subtree rooted at 2 is a BST and its size is 3.

##### Sample Input 2 :
50 -1 20 -1 30 -1 40 -1 50 -1 -1
4
##### Constraints :
1 <= 'N' <= 10^5
0 <= 'data' <= 10^5

where 'N' is the number of nodes and 'data' denotes the node value of the binary tree nodes.

Time limit: 1 sec
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