Lead Software Engineer

Given a binary tree of nodes 'N', you need to modify the value of its nodes, such that the tree holds the Children sum property.

A binary tree is said to follow the children sum property if, for every node of that tree, the value of that node is equal to the sum of the value(s) of all of its children nodes( left child and the right child).

Note :

 1. You can only increment the value of the nodes, in other words, the modified value must be at least equal to the original value of that node.
 2. You can not change the structure of the original binary tree.
 3. A binary tree is a tree in which each node has at most two children.      
 4. You can assume the value can be 0 for a NULL node and there can also be an empty tree.

You are given an arbitrary binary search tree (BST) with N nodes numbered 1 to N, and each node is associated with a value. You are also given Q queries, each of the Q queries are of the form [ L, R ], your task is to find the number of nodes in the BST which lie in the range L to R for each query.

For example

You are given the following tree.

And you are given 3 queries as follows
Q1 = [ 2 , 12 ]
Q2 = [ 10 , 50 ]
Q3 = [ 14 , 20 ] 

Then the answers for them will be as follows.
Answer for Q1 = 3 i.e. nodes 5, 10 , 12.
Answer for Q2 = 6 i.e. nodes 10 , 12 , 15 , 19 , 20 , 28.
Answer for Q3 = 3 i.e. nodes 15 , 19 , 20. 

Note :

It is guaranteed that the tree given will be a binary search tree.
It is guaranteed that all the node values will be distinct.

You are given a square matrix of non-negative integers 'MATRIX'. Your task is to rotate that array by 90 degrees in an anti-clockwise direction using constant extra space.

For example:

For given 2D array :

    [    [ 1,  2,  3 ],
         [ 4,  5,  6 ],
         [ 7,  8,  9 ]  ]

After 90 degree rotation in anti clockwise direction, it will become:

    [   [ 3,  6,  9 ],
        [ 2,  5,  8 ],
        [ 1,  4,  7 ]   ]

Que 1: What is class and object? Why the concept of class needed?
Que 2: Properties of OOPs
 

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