Paytm Software Engineer Interview Questions, Process, and Tips

Q1. ZigZag Traversal of Binary Tree
Ans. 
Zigzag traversal of a binary tree involves traversing the tree in a zigzag pattern, alternating between left and right at each level.
• Use a queue to perform level order traversal of the binary tree.

• For each level, alternate between adding nodes to the result array from left to right and right to left.

• Continue this pattern until all levels have been traversed.
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Q2. OOPs Concepts - Polymorphism, Inheritance
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Q3. DBMS Concepts and some SQL queries
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Q4. Java concepts like threading and some syntaxes
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Q1. Give 5 strengths and weakness of yours
Ans. 
Strengths: Problem-solving skills, teamwork, adaptability, attention to detail, communication. Weaknesses: Impatience, public speaking, delegation, perfectionism, time management.
• Strengths: Problem-solving skills - I enjoy tackling complex issues and finding creative solutions.

• Teamwork - I work well with others and value collaboration in achieving common goals.

• Adaptability - I am able to quickly adjust to new situation...read more
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Q2. Cross questions on answer of first question related to the role
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Q3. Will you be comfortable to work in a environment where releases does take place in night and engineers need to provide support at that time
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Q1. Basic SQL understanding ETL pipelines Reporting tools
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3 questions were asked that were easy to medium related to array, linked list and string

Q1. Internal working of hashmap
Ans. 
HashMap is a data structure that stores key-value pairs and uses hashing to quickly retrieve values based on keys.
• HashMap internally uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to determine the index in the array where it will be stored.

• If multiple keys hash to the same index, a collision occurs and the key-value pairs are stored in a linked list at that inde...read more
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Q2. Detect cycle in linked list
Ans. 
Use Floyd's Tortoise and Hare algorithm to detect cycle in a linked list.
• Initialize two pointers, slow and fast, at the head of the linked list.

• Move slow pointer by one step and fast pointer by two steps.

• If they meet at any point, there is a cycle in the linked list.
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Interviewer asked for the upi design

Online assement was on a platform which I don't remember at the moment
But it had 3 basic questions around DSA , try to write quality code as much as possible as questions were easy and doable by everyone

Q1. Check wether a given binary tree is a BST or not
Ans. 
To check if a binary tree is a BST, we can perform an in-order traversal and ensure that the elements are in sorted order.
• Perform an in-order traversal of the binary tree

• Check if the elements are in sorted order

• If any element is not in sorted order, then the tree is not a BST
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Q2. Merge sort using Linked list ( psuedo code )
Ans. 
Merge sort using linked list is a sorting algorithm that divides the list into smaller sublists, sorts them, and then merges them back together.
• Create a function to merge two sorted linked lists

• Divide the linked list into two halves using slow and fast pointers

• Recursively sort the two halves

• Merge the sorted halves back together
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Q1. Stack question of next greater element
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Q2. Gfg Puzzle around some horse
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Puzzles and DSA and OOPS concepts

Data Structures and Algorithms

Data Structures and Algorithms, OOPS

Duration : 1 Hr
No. of Questions : 3
Topics : Array, Greedy

Q1. Heap Related Question
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Q2. Convert BST in range
Ans. 
Convert a Binary Search Tree (BST) into a new BST containing only nodes within a given range.
• Perform inorder traversal of the original BST and only add nodes within the given range to the new BST.

• Recursively call the function on left and right subtrees while checking the node values against the range.

• Adjust the pointers of the nodes to form the new BST.
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Q1. What you like in cricket. Give 3 reasons.
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Q2. What are you planning for your future like studies and all.
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Python, SQL related questions

Q1. SQL, Python related
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Q2. Spark internals
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Q1. SQL, Python related
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Q2. Spark internals
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Q1. General managerial questions
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