SDE - 1

Given an array of integers of size ‘N’ and a positive integer ‘K’. Return the number of non-empty subarrays whose sum is divisible by K.

A subarray is a contiguous subset of an array.

For Example :

Consider an array of size four. The elements of the array are { -4, 5, 6, 1}. 
The value of K is 4. 
The subarrays whose sum is divisible by 4 are as  follows:
[ -4 ] 
[-4, 5, 6, 1] 
[ 5, 6, 1] 
Hence, there are three subarrays whose sum is divisible by 4. 

You are given a binary tree having 'n' nodes.

The boundary nodes of a binary tree include the nodes from the left and right boundaries and the leaf nodes, each node considered once.

Figure out the boundary nodes of this binary tree in an Anti-Clockwise direction starting from the root node.

Example :

Input: Consider the binary tree A as shown in the figure:

Output: [10, 5, 3, 7, 18, 25, 20]

Explanation: As shown in the figure

The nodes on the left boundary are [10, 5, 3]

The nodes on the right boundary are [10, 20, 25]

The leaf nodes are [3, 7, 18, 25].

Please note that nodes 3 and 25 appear in two places but are considered once.

Given an integer array 'NUMS' of size 'N' and an integer 'K'.

Return the number of good subarrays of 'NUMS'.

A subarray 'ARR' is good if there are at least 'K' pairs of indices (i, j) such that i < j and ARR[i] == ARR[j].

A subarray is a contiguous non-empty sequence of elements within an array.

For Example :

Let 'N' = 5, 'NUMS' = [1, 2, 1, 1, 3], K = 2.
Consider the subarray [1, 2, 1, 1] (indices 0 to 3 of NUMS). The elements are 1, 2, 1, 1.
Pairs with equal values and i < j within this subarray are:
(1 at index 0, 1 at index 2), (1 at index 0, 1 at index 3), (1 at index 2, 1 at index 3).
There are 3 such pairs. Since 3 >= K (2), this subarray is good.

Consider the subarray [1, 2, 1, 1, 3] (indices 0 to 4 of NUMS). The elements are 1, 2, 1, 1, 3.
Pairs with equal values and i < j within this subarray are:
(1 at index 0, 1 at index 2), (1 at index 0, 1 at index 3), (1 at index 2, 1 at index 3).
There are 3 such pairs. Since 3 >= K (2), this subarray is good.

Consider the subarray [2, 1, 1] (indices 1 to 3 of NUMS). The elements are 2, 1, 1.
Pairs with equal values and i < j within this subarray are:
(1 at index 1, 1 at index 2).
There is 1 such pair. Since 1 < K (2), this subarray is not good.

It can be shown that the only good subarrays are [1, 2, 1, 1] and [1, 2, 1, 1, 3].
Therefore, the total number of good subarrays is 2.

Questions on Java programming language like: (Learn)
1. Call by value vs call by reference
2. Java memory structure - stack, heap, string space, etc
3. Streams - pros and cons

Questions on Operating System like: (Learn)

4. Multithreading and multiprocessing + race condition
 

5. Questions on my previous projects

Asked me to design low-level design of ride hailing app (like Uber/Ola). Had to include the basic APIs to search a ride, book/create a ride, cancel a ride and update a ride. Pricing algo was to be very basic. Had to start with booking of 4-wheeler cabs and then extend it to 2-wheelers. (Learn)

Asked basic questions on my design and ways to make it more scalable and extensible. Then turned the discussion towards my projects and challenges I faced while working on them. These include my past company projects as well. (Learn)