Myntra Software Developer Interview Questions, Process, and Tips

Q1. 2 coding questions (arrays and tree) Oops concepts
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Q1. Right view of a Tree
Ans. 
The right view of a tree shows the nodes that are visible when looking at the tree from the right side.
• The right view of a tree can be obtained by performing a level order traversal and keeping track of the rightmost node at each level.

• Example: For a tree with nodes 1, 2, 3, 4, 5, the right view would be 1, 3, 5.
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Q1. 3 sum Trapping rain water
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3 sum and trapping rain water are common coding interview questions that test problem-solving skills.
• 3 sum problem involves finding three numbers in an array that add up to a target sum.

• Trapping rain water problem involves calculating the amount of water that can be trapped between bars in an elevation map.

• Both problems require efficient algorithms to solve.
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Q1. Linked List in a binary tree
Ans. 
A linked list can be implemented in a binary tree by using the left child as the next node and the right child as the previous node.
• Each node in the binary tree will have a left child pointer and a right child pointer.

• Traversal of the linked list can be done by following the left child pointers.

• Example: In a binary tree, the left child of a node can point to the next node in the linked list.
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Q1. Implement LRU cache
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LRU cache is a data structure that stores the most recently used items, discarding the least recently used items when full.
• Use a combination of a doubly linked list and a hashmap to efficiently implement LRU cache.

• When an item is accessed, move it to the front of the linked list to mark it as the most recently used.

• When adding a new item, check if the cache is full. If so, remove the least recently used item from the e...read more
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Q1. Mostly behavioural questions
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Round duration - 60 minutes
Round difficulty - Easy

This was a online coding interview where I was asked coding questions.

Q1. 
Preorder Traversal of a BST Problem Statement
Given an array PREORDER representing the preorder traversal of a Binary Search Tree (BST) with N nodes, construct the original BST.
Each element in the given...read more
Ans. 
Preorder traversal is: process the root, left subtree, and then right subtree. So, to emulate this behaviour in a non-recursive way, a stack can be used. 
1. Start with pushing the root node to the stack and continue the traversal till there is at least one node onto the stack. 2. Pop the root node from stack, process it and push it’s right and left child on to stack. We push the right child before the left child b...read more
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Q2. 
Convert Sorted Array to BST Problem Statement
Given a sorted array of length N, your task is to construct a balanced binary search tree (BST) from the array. If multiple balanced BSTs are possible, you ca...read more
Ans. 
The approach to this question is quite simple. We traverse the array and process each element one by one. We separately create an insert function which basically takes the root node and the array element as parameters and insert the element in the tree after evaluating the conditions: 
1.Start from the root. 
2. Compare the inserting element with root, if less than root, then recurse for left, else recurse for ...read more
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Round duration - 60 minutes
Round difficulty - Easy

This was a technical round. Programming based questions and oops/dbms based were asked. 
Some questions were :
1. How many types of trigger?
Ans. In SQL, there are 3 types of triggers :
DML (data manipulation language) triggers – Eg.– INSERT, UPDATE, and DELETE
DDL (data definition language) triggers Eg.– CREATE, ALTER, and DROP
Logon triggers –This type reacts to LOGON events
2. Can trigger be used with select statement?
Ans. No, triggers cannot be used with select statements. They can only be used with Insert, update or delete statements. 
3. Indexing in mysql? How many types of indexing in mysql?
Ans. Indexes are used to find rows with specific column values quickly. It helps to determine the position to seek to in the middle of the data file without having to look at all the data. It performs much faster than reading every row sequentially.
4. Engines in mysql?
Ans. So, in mysql, storage engine is a software module that a database management system uses to create, read, update data from a database. There are two types of storage engines: transactional and non-transactional.
5. Singleton pattern?
Ans. Singleton is a creational design pattern that ensured that a class has only one instance, while providing a global access point to this instance.

Q1. 
Pair Sum Problem Statement
You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to find and return a list of all pairs of elements where each sum of a pair equals 'S'.
Note:
...read more
Ans. 
The problem can be solved in O(n) time using the concept of hashing. 
Use a hashset to check for the current array value. Check if targetsum – current value exists in the map or not. If it exists, that means a pair with sum equal to target sum exists in the array.
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Round duration - 120 minutes
Round difficulty - Easy

This was a 2 hour round consisting of 5 mcqs and 2 codes. The mcqs were pretty much simple based on DS, DBMS, OS, OOP, and C language.

Q1. 
Binary Tree to Doubly Linked List
Transform a given Binary Tree into a Doubly Linked List.
Ensure that the nodes in the Doubly Linked List follow the Inorder Traversal of the Binary Tree.
Input:
The fi...read more
Ans. 
If the left subtree exists, recursively convert the left subtree to Doubly Linked List.
If the right subtree exists, recursively convert the right subtree to Doubly Linked List.
When in the left subtree, find the inorder predecessor of the root, make this as the previous of the root and its next as the root.
Similarly, when in the right subtree, find the inorder successor of the root, make this as the next of the root and...read more
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Q2. 
Validate BST Problem Statement
Given a binary tree with N nodes, determine whether the tree is a Binary Search Tree (BST). If it is a BST, return true; otherwise, return false.
A binary search tree (BST)...read more
Ans. 
A simple O(N) approach for this question would be :
1. Do an inorder traversal of the tree and store all the values in a temporary array. 
2. Next, check if the array is sorted in ascending order or not.
3. If it is sorted, the given tree is a BST. 
The above approach uses an auxiliary array. In order to avoid using auxiliary array :
1. Maintain track of the previously visited node in a variable prev. 
2. Next...read more
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Round duration - 60 minutes
Round difficulty - Easy

3 coding questions were asked in this round.

Q1. 
Sort an Array in Wave Form
You are given an unsorted array ARR. Your task is to sort it so that it forms a wave-like array.
Input:
The first line contains an integer 'T', the number of test cases.
For ea...read more
Ans. 
This question can be solved using any sorting algorithm.
1. Sort the array first so that all the elements are arranged in increasing order. 
A[0]<=A[1]<=A[2]<=A[3]…. A[n-1]
2. Next, pick the elements in pairs from the start and swap the adjacent elements. This will arrange the array in the wave form. 
The time complexity of this approach would be O(nlogn). 
For a more optimized approach, On observing...read more
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Q2. 
Problem: Search In Rotated Sorted Array
Given a sorted array that has been rotated clockwise by an unknown amount, you need to answer Q queries. Each query is represented by an integer Q[i], and you must ...read more
Ans. 
This question could be solved using Binary search which would have a time complexity of O(log n). 
The approach would be: 
1.Find the mid = (low + high)/2
2.If key is present at middle point, return mid.
3. If arr[low….mid] is sorted
a) If key to be searched lies in range from arr[low] to arr[mid], apply binary search for arr[low..mid].
b) Else apply for arr[mid+1..high]
4. Else (arr[mid+1..high] must be sorted)
a) I...read more
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Q3. 
Running Median Problem
Given a stream of integers, calculate and print the median after each new integer is added to the stream.
Output only the integer part of the median.
Example:
Input:
N = 5  
Stre...read more
Ans. 
To solve this question, the concept of heaps can be used. Two heaps can be maintained: a max heap for storing lower half of the numbers and a min heap for storing greater half of the numbers.
Process each element one by one.
1. To add an element to one of the heaps:
Check if next item is smaller than maxHeap root add it to maxHeap, else add it to minHeap
2: Balance the heaps (after this step heaps will be either balanced o...read more
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Round duration - 60 minutes
Round difficulty - Medium

It was a 60 minute online coding interview where programming questions were discussed.

Q1. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. 
This can be solved both: recursively and iteratively. 
The recursive approach is more intuitive. First reverse all the nodes after head. Then we need to set head to be the final node in the reversed list. We simply set its next node in the original list (head -> next) to point to it and sets its next to NULL. The recursive approach has a O(N) time complexity and auxiliary space complexity. 

For solving the q...read more
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Q2. 
Rearrange Array: Move Negative Numbers to the Beginning
Given an array ARR consisting of N integers, rearrange the elements such that all negative numbers are located before all positive numbers. The orde...read more
Ans. 
The naive approach would be to use an auxiliary array. Copy all elements to that array. Copy all negative elements first to the original array and then all positive elements. This approach would have a time complexity of O(N) but also uses O(N) auxiliary space. 
For constant space, we first count total negative numbers. 
Then till all negative numbers are moved to the beginning, traverse the array. Swap the pos...read more
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Round duration - 60 minutes
Round difficulty - Easy

Questions based on data structures , OOPS , Java and operating systems were discussed.

Q1. 
Convert a Binary Tree to its Sum Tree
Given a binary tree of integers, convert it to a sum tree where each node is replaced by the sum of the values of its left and right subtrees. Set leaf nodes to zero.
...read more
Ans. 
The question can be solved recursively in O(N) time complexity and O(N) auxiliary space complexity. 
Store the initial value of the node in a variable. 
Next, Recursively call for left and right subtrees and change the value of the current node as sum of the values returned by the two recursive calls.
At last, return the sum of new value and the initial value.
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Q2. Can you explain the concept of the String pool in Java and how garbage collection functionality works?
Ans. 
String Pool in java is a pool of Strings stored in Java Heap Memory. String pool helps in saving a lot of space for Java Runtime although it takes more time to create the String. String Pool is possible only because String is immutable in Java and its implementation of String interning concept. String pool is also an example of Flyweight design pattern.
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Q3. How can you synchronize a HashMap in Java?
Ans. 
HashMap is a non-synchronized collection class. So, we need to explicitly synchronise them. HashMap can be synchronized using the Collections.synchronizedMap() method. It returns a thread-safe map backed up by the specified HashMap. In order to guarantee serial access, it is critical that all access to the backing map is accomplished through the returned map.
Syntax: public static Map synchronizedMap(Map m)
Parameters: T...read more
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Round duration - 45 minutes
Round difficulty - Medium

This was CTO round, if you make this round…you are doing pretty good. 
He asked a lot on what I worked on and asked questions relevant to that. Process thread, stacks heaps. A minor system design on component in their system. How they are shared between and trade-off. We discussed about scalability and challenge.

Q1. Can you explain the differences between one-to-one mapping and one-to-many mapping in database design, along with some basic related questions?
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Q2. What is the difference between a process and a thread?
Ans. 
A process is an instance of a program that is being executed. Thread is a lightweight process that is managed by the scheduler independently. For Eg : Opening a new browser is a process while opening multiple tabs in a browser is thread. 
Processes are independent of each other while threads are interdependent and share memory.
Each process is treated as a new process by the operating system while with threads. the ...read more
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