30+ PubMatic Interview Questions and Answers

Implement a function to print the zigzag traversal of a Binary Tree.

• Traverse the Binary Tree level by level, alternating the direction of traversal for each level.

• Use a queue to keep track of nodes at each level and a flag to switch the direction of traversal.

• Print the values of nodes in the zigzag order as described in the problem statement.

I prefer Python because of its simplicity, readability, and extensive libraries.

• Python is known for its simplicity and readability, making it easier to write and understand code.

• Python has a large number of libraries and frameworks that can be used to quickly develop applications.

• Python's syntax is clean and concise, allowing for faster development and easier maintenance.

• Python is widely used in various domains such as web development, data analysis, and machine learning.

• Pyth...read more

Calculate the time in minutes required to completely burn a binary tree starting from a given node.

• Start burning from the given node and spread fire to adjacent nodes each minute

• Track the time taken for each node to burn completely

• Return the maximum time taken to burn the entire tree

To solve the issue of mistakenly assigned gender values in SQL, you can update the incorrect values using SQL queries.

• Identify the incorrect gender values in the SQL table

• Use UPDATE statement with appropriate conditions to correct the values

• For example, if 'F' is mistakenly assigned for male, update it to 'M' using UPDATE statement

Count the number of trailing zeros in the factorial of a given number.

• Count the number of factors of 5 in the factorial of the given number N.

• Divide N by 5, then by 25, then by 125, and so on, and sum up the quotients to get the total number of trailing zeros.

• Example: For N=10, 10/5=2, so there are 2 factors of 5 in 10!, hence 2 trailing zeros.

Determine the maximum amount of money a thief can steal from houses without looting two consecutive houses.

• Use dynamic programming to keep track of the maximum money that can be stolen up to each house.

• At each house, the thief can either choose to steal from the current house or skip it and steal from the previous house.

• The maximum amount of money that can be stolen without looting two consecutive houses is the maximum of the two options.

Convert a binary tree into its mirror tree by interchanging left and right children of non-leaf nodes.

• Traverse the tree in a recursive manner and swap the left and right children of each node.

• Use a temporary variable to swap the children of each node.

• Ensure to modify the tree in place without creating a new tree.

• Example: For the input tree 1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1, the mirror tree will have inorder traversal as 7 4 2 1 6 3 5.

Implement a function to find any topological sorting of a Directed Acyclic Graph (DAG).

• Use Depth First Search (DFS) to find the topological ordering of the vertices.

• Start by visiting a vertex and recursively visit its adjacent vertices before adding it to the result array.

• Maintain a visited array to keep track of visited vertices and avoid cycles.

• Once all vertices are visited, reverse the result array to get the topological sort.

• Example: For a DAG with edges 0->1, 0->3, 1->2,...read more

Code using multithreading to scan 3 log files for different patterns and write matches in o/p file with low memory footprint.

• Use Python's threading module to create multiple threads for each log file

• Use regex to search for patterns in each log file

• Write matches to output file using a thread-safe queue

• Use a memory-efficient data structure like deque to store log file lines

Simulating one user profile to another can be done through user impersonation.

• User impersonation can be achieved through various tools and techniques.

• One way is to use a proxy server to intercept and modify the user's requests and responses.

• Another way is to use a browser extension or plugin that allows you to switch between user profiles.

• You can also use a testing tool like Selenium to automate the process of switching between user profiles.

• It's important to ensure that the ...read more

Code to run as a service to scan CPU/memory every 30 sec and calculate min, max, avg and moving avg of last 300 sec.

• Use a loop to run the code every 30 sec

• Use psutil library to get CPU/memory usage

• Store the values in a list and calculate min, max, avg and moving avg using numpy library

• Use threading to run the code in the background as a service

Count the occurrences of a particular word from a file.

• Read the file and store its contents in a string variable.

• Split the string into an array of words using a delimiter.

• Loop through the array and count the occurrences of the particular word.

• Return the count.

Multiprocessing is the use of multiple processors to execute multiple tasks simultaneously. Multithreading is the use of multiple threads within a single process to execute multiple tasks simultaneously.

• Multiprocessing involves the use of multiple processors or cores to execute multiple tasks simultaneously.

• Multithreading involves the use of multiple threads within a single process to execute multiple tasks simultaneously.

• Multiprocessing is typically used for CPU-intensive ta...read more

Implement a data structure like a hash table or a cache to optimize memory search.

• Use a hash table to store the data with keys as memory locations

• Implement a cache to store frequently accessed data for faster retrieval

• Consider using indexing or sorting techniques to optimize search operations

Code to validate all use cases for an IP address input string and output yes or no.

• Use regular expressions to match the input string against the valid IP address pattern.

• Check for valid ranges of each octet (0-255) and proper formatting (4 octets separated by periods).

• Handle edge cases like leading zeros, extra spaces, and invalid characters.

• Return 'yes' if the input string is a valid IP address, otherwise return 'no'.

Fluent wait in Selenium is used for handling dynamic elements and synchronization issues.

• Fluent wait is used to wait for a condition to be true before proceeding with the next steps in Selenium automation scripts.

• It provides more flexibility in defining wait conditions compared to implicit or explicit waits.

• Fluent wait can be used to wait for a specific element to be visible, clickable, or any other custom condition.

• It is not used as frequently because it can lead to longer e...read more

Count pairs in an array that sum up to a target value.

• Iterate through the array and store the frequency of each element in a hashmap.

• For each element, check if the difference between the target and the element exists in the hashmap.

• Increment the count of pairs if the difference is found in the hashmap.

Find common values in two sorted integer arrays efficiently.

• Use two pointers approach to iterate through both arrays simultaneously.

• If the current values are equal, add it to the result and move both pointers forward.

• If the current values are not equal, move the pointer of the array with the smaller value forward.

Implement a stack data structure using an array of strings.

• Use an array to store the strings in the stack.

• Implement push() and pop() functions to add and remove elements from the stack.

• Keep track of the top of the stack using a variable.

Binary search can be used to solve moderate problems of arrays that are first increasing and then decreasing.

• Use binary search to find the peak element in the array, which marks the transition from increasing to decreasing.

• Divide the array into two parts based on the peak element and apply binary search on each part separately.

• Handle edge cases such as when the array is strictly increasing or strictly decreasing.

• Example: ['1', '3', '5', '7', '6', '4', '2']

bashrc and .profile are configuration files for the Bash shell in Linux/Unix systems.

• bashrc is executed for every new interactive shell session

• .profile is executed only once during login

• They contain environment variables, aliases, and other shell settings

• bashrc is typically used for user-specific settings, while .profile is system-wide

• Examples: setting PATH variable, defining aliases, setting prompt

Find the smallest subarray in an array that has a given target sum.

• Use a sliding window approach to find the subarray with the target sum.

• Keep track of the current sum of elements in the window and adjust the window size accordingly.

• Start with a window of size 1 and expand it until the sum is greater than or equal to the target sum.

• Shrink the window from the left side while updating the smallest subarray length until the sum is less than the target sum.

To get all the links available on a page, you can use web scraping techniques.

• Use a web scraping tool like BeautifulSoup in Python or Selenium to extract all the links from the page

• Identify the HTML elements that contain the links, such as tags with href attributes

• Iterate through the elements to extract the URLs and store them in a list

The longest path from one node to another in a tree is the maximum number of edges that must be traversed to reach from one node to another.

• The longest path in a tree is also known as the diameter of the tree.

• The diameter of a tree can be found by first finding the farthest leaf node from any arbitrary node, and then finding the farthest leaf node from that leaf node.

• The sum of the distances from the root to the farthest leaf nodes in both subtrees of the root gives the diame...read more

Detecting a loop in a linked list

• Use two pointers, one moving at double the speed of the other

• If there is a loop, the two pointers will eventually meet

• Use Floyd's Cycle Detection Algorithm for efficient solution

Design a system for a web surfing utility

• Use a web crawler to gather data from websites

• Implement a search engine to retrieve relevant information

• Utilize a recommendation system to suggest related content

• Include user authentication and personalized settings

• Ensure scalability and performance for handling large amounts of data

Apache Kafka is a distributed streaming platform used for building real-time data pipelines and streaming applications.

• Apache Kafka is designed to handle high-throughput, fault-tolerant, and scalable real-time data streams.

• It allows for the publishing and subscribing to streams of records, similar to a message queue.

• Kafka is often used for log aggregation, stream processing, event sourcing, and real-time analytics.

• It provides durability and fault tolerance through replication...read more

Java code to reverse a string without using split method

• Create a char array from the input string

• Use two pointers to swap characters from start and end of the array

• Continue swapping until the pointers meet in the middle

Count the number of digits in a given string

• Iterate through each character in the string

• Check if the character is a digit using isdigit() function

• Increment a counter if the character is a digit

• Return the final count of digits

Java code to find duplicates in an array of strings

• Iterate through the array and use a HashSet to keep track of unique elements

• If an element is already in the HashSet, it is a duplicate

• Print or store the duplicates as needed

Designing a chess game involves creating a board with 64 squares, defining the movement rules for each piece, implementing game logic, and designing a user interface.

• Create a 8x8 board with alternating colors for squares

• Define movement rules for each type of chess piece (pawn, rook, knight, bishop, queen, king)

• Implement game logic for capturing pieces, checkmate, stalemate

• Design a user interface for players to interact with the game