PubMatic Interview Questions, Process, and Tips

Basic string manipulation and general DSA questions

Q1. Tree traversal iteratively
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Q2. Implement DFS,BFS on graph
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Q1. Java coding for array duplicates
Ans. 
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
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Q2. Java code for reverse string without split
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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
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Q1. Mostly towards your programming and coding ability. 1. Starting from DS, trees, algorithm, multi threading 2. Ask around strings and arrays
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Q2. 1. longest path from node to node in tree
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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 farthe...read more
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Q1. OS, In death problem solving questions, multi threading.
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Q2. 1. Process 2. Dynamic memory 3. segment corrupted recovery 4. design system to take billions of request
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Q1. Reverse link list
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Q2. Count number of digits
Ans. 
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
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Q1. What is Apache Kafka?
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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 p...read more
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Q1. How do you manage stress?
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Q1. Write a code in c c++ or any other language to validate all use cases for an ip address given as input string. Output will be yes or no.
Ans. 
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'.
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Q2. Given 2 sorted integer array print the common value between them. 2 to 3 optimized ways.
Ans. 
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.
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Q1. Basic DSA question on array, linked list, graph
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Q2. Loop in kinked list
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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
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Q1. Similar question on DSA and little bit details on previous work experince.
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Q1. Standard managerial round with focus on previous work
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LRU Cache impl, 3 threads....print 123123123..in sequence

Role & Responsibilities, Virtual Memory, IPC/Shared Memory, Stack/Heap, Reverse a number with sign, Memory Corruption, Memory pool of 1GB - how you will break it in chunks and provide on demand, GDB commands, Valgrind, C++11 features, Segmentaion fault - who generates core dump.