Paytm Technical Lead Interview Questions and Answers

DSA questions on graphs

Q1. Java multithreading,hibernate,kafka
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Q2. Make a method thread safe
Ans. 
Use synchronization mechanisms like locks or synchronized blocks to ensure only one thread can access the method at a time.
• Use synchronized keyword in method signature

• Use synchronized blocks inside the method

• Use ReentrantLock for more fine-grained control
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Q1. System Design question on async flow
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Q1. Salary negotation
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Q1. No i can't discuss
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Q2. Java multi threading,kafka microservices
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Had to implement 2 medium questions. and give approach for 1 hard level questions. Basic questions around java were also asked.

Q1. Design system for gaming android app like ludo.
Ans. 
Design a system for a gaming android app like ludo.
• Implement game logic for ludo including dice rolling, moving pieces, and winning conditions.

• Create a user interface with a game board, player pieces, and dice.

• Incorporate multiplayer functionality for online play.

• Include features like in-game chat, leaderboards, and customizable game settings.

• Utilize a backend server to handle game synchronization and data storage.
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Q1. Reverse the given linked list
Ans. 
Reversing a linked list involves changing the direction of its nodes to point to the previous node instead of the next.
• Initialize three pointers: prev (null), current (head), and next (null).

• Iterate through the list: while current is not null, set next to current.next.

• Change current.next to prev, then move prev and current one step forward.

• Repeat until current is null; prev will be the new head of the reversed list.

• Exa...read more
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Q2. Separate out 0's, 1's, and 2's in an array
Ans. 
Separate out 0's, 1's, and 2's in an array
• Create three variables to count the number of 0's, 1's, and 2's in the array

• Loop through the array and increment the respective variable for each occurrence

• Create a new array and add the counted number of 0's, 1's, and 2's in order
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Q1. Remove duplicates from the given array
Ans. 
Remove duplicates from given array of strings
• Create a new empty array

• Loop through the original array and check if the element already exists in the new array

• If not, add it to the new array

• Return the new array
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Q2. Detect a loop in linked list
Ans. 
Loop in linked list can be detected using Floyd's cycle-finding algorithm.
• Floyd's cycle-finding algorithm uses two pointers, one moving at twice the speed of the other.

• If there is a loop, the faster pointer will eventually catch up to the slower pointer.

• If there is no loop, the faster pointer will reach the end of the list.

• Time complexity of this algorithm is O(n) and space complexity is O(1).
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