JioStar Android Developer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Easy

Technical interview round. I was asked 2 DSA problems to discuss and code.

Q1. 
Binary Array Sorting Problem Statement
You are provided with a binary array, i.e., an array containing only 0s and 1s. Your task is to sort this binary array and return it after sorting.
Input:
 The fir...read more
Ans. 
Yes, the binary array sorting problem can be solved in linear time and constant space by using a two-pointer approach.
• Use two pointers, one starting from the beginning of the array and the other starting from the end.

• Swap 0s to the left side and 1s to the right side by incrementing and decrementing the pointers accordingly.

• Continue this process until the two pointers meet in the middle of the array.

• Example: Input: [1,
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Q2. 
Maximum Subarray Sum Problem Statement
Given an array arr of length N consisting of integers, find the sum of the subarray (including empty subarray) with the maximum sum among all subarrays.
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Ans. 
Find the sum of the subarray with the maximum sum among all subarrays in a given array.
• Iterate through the array and keep track of the maximum sum subarray encountered so far.

• Use Kadane's algorithm to efficiently find the maximum subarray sum.

• Consider the case where all elements in the array are negative.

• Handle the case where the array contains only one element.
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Round duration - 60 minutes
Round difficulty - Medium

Technical interview round. I was asked questions related to Android and its architecture.

Q1. How does RecyclerView work internally?
Ans. 
RecyclerView is a flexible view for providing a limited window into a large data set.
• RecyclerView recycles views to improve performance and memory usage.

• It uses a LayoutManager to organize and position items within the view.

• Adapter provides data to be displayed in the RecyclerView.

• ItemDecoration allows for custom drawing of item decorations like borders or dividers.
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Q2. Can you explain how to implement a ViewModel in Android?
Ans. 
ViewModel in Android is a class that is responsible for preparing and managing data for an activity or fragment.
• ViewModel is part of the Android Architecture Components and is used to store and manage UI-related data in a lifecycle-conscious way.

• It survives configuration changes such as screen rotations and retains data during the lifecycle of the activity or fragment.

• ViewModel should never hold a reference to a view o...read more
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Round duration - 60 minutes
Round difficulty - Easy

Round duration - 50 minutes
Round difficulty - Easy

Round duration - 60 minutes
Round difficulty - Easy

At the beginning of this round, the interviewer asked me about the data structures I knew. Linked lists, trees, graphs, arrays etc. was my answer. He asked me how well I knew Dynamic Programming. I said I wasn’t strong in that and he said that he would ask me a question on dynamic programming for sure.

Round duration - 40 minutes
Round difficulty - Easy

The interviewer asked me if I was comfortable with the interview process so far and how the previous interviews were. I said it was good and he gave me the first problem to solve.

Round duration - 60 minutes
Round difficulty - Easy

The interviewer asked me some Com­puter Sci­ence‍ fundamentals in this round as well as some behavioural questions.

Q1. Implement a Trie data structure and write functions to insert and search for a few words in it.
Ans. 
Implement a Trie data structure with insert and search functions.
• Create a TrieNode class with children and isEndOfWord attributes.

• Implement insert function to add words by iterating through characters.

• Implement search function to check if a word exists by traversing the Trie.

• Example: Insert 'apple', 'banana', 'orange' and search for 'apple' and 'grape'.
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Round duration - 90 minutes
Round difficulty - Medium

 Around 65-70 people sat for the test. 15 people were shortlisted. It consisted of the following to be done in 90 minutes.

- 28 MCQs based on core CS 

- 2 Coding questions – everyone had different and random questions. Most questions were custom logic based (easy level) including some standard questions – LCS, LIS, topological sort.

Round duration - 60 minutes
Round difficulty - Easy

Interviewer was very friendly. It started with the standard – tell me about yourself / introduce yourself type of question. Then he proceeded and asked two coding questions

Q1. 
Remove Duplicates from a Sorted Linked List
Your friend has homework to complete. Help him by removing duplicates from a sorted linked list.
You are given the 'Head' of a sorted linked list. Modify the l...read more
Ans. 
Remove duplicates from a sorted linked list without adjacent duplicates.
• Traverse the linked list while comparing current and next nodes.

• If they are equal, skip the next node by updating the current node's next pointer.

• Repeat until the end of the list is reached.
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Q2. 
Course Schedule Problem Statement
You are enrolled as a student and must complete N courses, numbered from 1 to N, to earn your degree.
Some courses have prerequisites, which means that to take course i,...read more
Ans. 
Check if it is feasible to complete all courses with prerequisites.
• Create a graph representing the prerequisites with courses as nodes and edges as prerequisites.

• Perform a topological sort on the graph to check if there is a cycle (if there is, then it's not feasible to complete all courses).

• If there is no cycle, then it is feasible to complete all courses.
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Round duration - 60 minutes
Round difficulty - Medium

This round had only 1 question. The interviewer introduced himself. And he advised me to clearly understand the problem before proceeding.

Q1. 
LCA of Binary Tree Problem Statement
You are given a binary tree of distinct integers, along with two nodes, ‘X’ and ‘Y’. Your task is to determine the Lowest Common Ancestor (LCA) of ‘X’ and ‘Y’.
The LC...read more
Ans. 
Find the Lowest Common Ancestor of two nodes in a binary tree.
• Traverse the binary tree to find the paths from the root to nodes X and Y.

• Compare the paths to find the last common node, which is the Lowest Common Ancestor.

• Implement a recursive function to efficiently find the LCA.

• Handle cases where one node is an ancestor of the other.

• Consider edge cases like when X or Y is the root node.
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Round duration - 60 minutes
Round difficulty - Medium

Pretty Good Round. Fast Paced. We covered a lot of ground.

Q1. 
Binary Search Tree Iterator Problem Statement
Design and implement a class BSTIterator to perform an in-order traversal over a Binary Search Tree (BST). Your implementation should include the following me...read more
Ans. 
Design and implement a class BSTIterator to perform in-order traversal over a Binary Search Tree (BST).
• Implement a parameterized constructor to initialize the iterator with the root of the BST.

• Implement a method 'next()' to return the next smallest element in in-order traversal.

• Implement a method 'hasNext()' to check if there exists a next smallest element in traversal.

• Ensure the output is the in-order traversal of the
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Q2. 
Maximum Consecutive Ones Problem Statement
Given a binary array 'ARR' of size 'N', your task is to determine the maximum length of a sequence consisting solely of 1’s that can be obtained by converting at...read more
Ans. 
Find the maximum length of a sequence of 1's by converting at most K zeroes into ones in a binary array.
• Iterate through the array and keep track of the current window of 1's and zeroes.

• Use a sliding window approach to find the maximum length of consecutive 1's by flipping at most K zeroes.

• Update the window based on the number of zeroes flipped and keep track of the maximum length found so far.

• Return the maximum length ...read more
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Q3. 
BFS in Graph Problem Statement
You are given an undirected and disconnected graph G(V, E) having V vertices numbered from 0 to V-1 and E edges. Your task is to print its BFS traversal starting from the 0t...read more
Ans. 
BFS traversal of an undirected and disconnected graph starting from vertex 0.
• Start BFS traversal from vertex 0 and visit all connected nodes in sorted order.

• Use a queue to keep track of nodes to visit next.

• Keep a visited array to avoid revisiting nodes.

• Print the BFS traversal path as the nodes are visited.

• Example: For input V=5, E=4 and edges 0-1, 0-2, 1-3, 2-4, the BFS traversal will be [0, 1, 2, 3, 4].
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Q4. 
Dijkstra's Shortest Path Problem Statement
Given an undirected graph with V vertices (labeled 0, 1, ..., V-1) and E edges, each edge connects two nodes X and Y with a specified weight representing the dis...read more
Ans. 
Dijkstra's algorithm is used to find the shortest path distance from a source node to all other nodes in an undirected graph.
• Implement Dijkstra's algorithm to find the shortest path distance from node 0 to all other nodes in the graph.

• Use a priority queue to efficiently select the next node with the shortest distance.

• Initialize distances to all nodes as infinity, except for the source node which is 0.

• Update distances t...read more
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Round duration - 60 minutes
Round difficulty - Hard

Bar Raised Round. Definitely felt the difficulty.

Q1. 
First Non-Repeating Character Problem Statement
You are given a string consisting of English alphabet characters. Your task is to identify and return the first character in the string that does not repeat...read more
Ans. 
Identify and return the first non-repeating character in a string, or the first character if all characters repeat.
• Iterate through the string to count the frequency of each character

• Iterate through the string again to find the first character with frequency 1

• If no such character is found, return the first character of the string
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Round duration - 90 Minutes
Round difficulty - Medium

Interview started at 11:00 am. It was an online round. During the coding round I submitted optimized solution and got full acceptance of the solutions.

Q1. 
Detect Cycle in a Directed Graph
You are provided with a directed graph composed of 'N' nodes. You have a matrix called 'EDGES' with dimensions M x 2, which specifies the 'M' edges in the graph. Each edge...read more
Ans. 
Detect cycle in a directed graph using depth-first search (DFS) algorithm.
• Use DFS to traverse the graph and detect back edges indicating a cycle.

• Maintain a visited array to keep track of visited nodes during traversal.

• If a node is visited again during traversal and it is not the parent node, then a cycle exists.

• Return true if a cycle is detected, false otherwise.
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Round duration - 80 Minutes
Round difficulty - Medium

Interview started at 10:00 am. Interview went well, I was able to connect with the interviewer and enjoyed the whole interview

Q1. 
Next Smallest Palindrome Problem Statement
Find the next smallest palindrome strictly greater than a given number 'N' represented as a string 'S'.
Explanation:
You are given a number in string format, a...read more
Ans. 
Find the next smallest palindrome greater than a given number represented as a string.
• Convert the string to an integer, find the next greater palindrome, and convert it back to a string.

• Handle cases where the number is a palindrome or has all digits as '9'.

• Consider both odd and even length numbers when finding the next palindrome.
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Round duration - 80 Minutes
Round difficulty - Medium

Interview started at 11:00 am. Interview went well.

Q1. 
Boundary Traversal of a Binary Tree
Given a binary tree of integers, your task is to return the boundary nodes of the tree in Anti-Clockwise direction starting from the root node.
Input:
The first line ...read more
Ans. 
Return the boundary nodes of a binary tree in Anti-Clockwise direction starting from the root node.
• Traverse the left boundary nodes in a top-down manner

• Traverse the leaf nodes from left to right

• Traverse the right boundary nodes in a bottom-up manner

• Handle cases where duplicates occur in the boundary nodes

• Implement the function without printing as printing is already managed
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Round duration - 90 minutes
Round difficulty - Easy

This was MCQ+Coding round.

Q1. How can you check if two strings are anagrams of each other?
Ans. 
Check if two strings are anagrams by comparing the sorted versions of the strings.
• Sort both strings and compare if they are equal.

• Use a hashmap to store the frequency of characters in each string and compare the maps.

• Ignore spaces and punctuation when comparing the strings.
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Round duration - 90 minutes
Round difficulty - Easy

This was face to face interview round.

Round duration - 90 minutes
Round difficulty - Easy

This was face to face interview round.

Round duration - 60 minutes
Round difficulty - Easy

I had one interview for approx. an hour, it includes both Technical and HR round, well mostly technical. Interview starts with tell me something about yourself. Asked in detailed about algorithms/web based projects mentioned in CV, make sure that whatever you have written you have complete knowledge about it. Asked to code few basic algorithms questions. Do mention about small project if you have done related to web development.
If interviewer says if you want to ask any question, its always better to ask one or two question.

Q1. Can you introduce yourself?
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Q2. What is a Binary Search Tree (BST)?
Ans. 
A Binary Search Tree (BST) is a data structure where each node has at most two children, with the left child being less than the parent and the right child being greater.
• Nodes in a BST are arranged in a hierarchical order where the left subtree of a node contains only nodes with keys less than the node's key, and the right subtree contains only nodes with keys greater than the node's key.

• BST allows for efficient search...read more
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Q3. 
Binary Search Tree Insertion
Given the root node of a binary search tree and a positive integer, you need to insert a new node with the given value into the BST so that the resulting tree maintains the pr...read more
Ans. 
Insert a new node with a given value into a binary search tree while maintaining the properties of a BST.
• Traverse the BST starting from the root node and compare the value to be inserted with each node's value to determine the correct position for insertion.

• Insert the new node as a leaf node in the appropriate position to maintain the BST properties.

• Ensure that the resulting tree is a valid binary search tree by follow...read more
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Q4. 
Delete Node in Binary Search Tree Problem Statement
You are provided with a Binary Search Tree (BST) containing 'N' nodes with integer data. Your task is to remove a given node from this BST.
A BST is a ...read more
Ans. 
Delete a given node from a Binary Search Tree (BST) and return the inorder traversal of the modified BST.
• Traverse the BST to find the node to be deleted.

• Handle different cases like node with no children, one child, or two children.

• Update the pointers of the parent node and child nodes accordingly.

• Perform inorder traversal after deletion to get the modified BST.
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Q5. 
Clone Linked List with Random Pointer Problem Statement
Given a linked list where each node has two pointers: one pointing to the next node and another which can point randomly to any node in the list or ...read more
Ans. 
Yes, the cloning of a linked list with random pointer can be accomplished without utilizing extra space.
• Use a hashmap to store the mapping between original nodes and their corresponding cloned nodes.

• Iterate through the original linked list to create the cloned nodes and update the hashmap.

• Iterate through the original linked list again to set the next and random pointers of the cloned nodes using the hashmap.

• Time comple...read more
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