Amazon Transportation Services Senior Technical Support Engineer 2 Interview Questions and Answers

Q1. About the experience and what I did
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Give me a palindrom of string related question

Q1. System design based on how to scale something
Ans. 
To scale a system, consider horizontal and vertical scaling, load balancing, caching, database sharding, and microservices architecture.
• Implement horizontal scaling by adding more instances of the application to distribute the load.

• Consider vertical scaling by upgrading the hardware resources of the existing server.

• Use load balancing to evenly distribute incoming network traffic across multiple servers.

• Implement cachin...read more
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Q1. Given a string, find the longest length palindromic substring in the given string.
Ans. 
Find the longest palindromic substring in a given string.
• Use dynamic programming to solve the problem efficiently.

• Start with the base cases of single characters and two characters.

• For longer substrings, check if the first and last characters match and if the substring between them is also a palindrome.

• Keep track of the longest palindrome seen so far.

• Time complexity: O(n^2), space complexity: O(n^2).
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Q1. Mention the most challenging technical problem you had to solve.
Ans. 
Developing a real-time data processing system for a high-traffic website.
• Designing a scalable architecture to handle the high volume of incoming data.

• Optimizing the data processing algorithms to minimize latency.

• Ensuring data consistency and accuracy in a distributed system.

• Implementing fault-tolerant mechanisms to handle system failures.

• Testing and debugging the system under various load conditions.
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Q2. Some minor low level entity design.
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Round duration - 120 minutes
Round difficulty - Medium

Due to pandemic placement process went virtual. Test was conducted at 10 A.M.

Q1. 
Decode String Problem Statement
Your task is to decode a given encoded string back to its original form.
Explanation:
An encoded string format is <count>[encoded_string], where the 'encoded_string...read more
Ans. 
The task is to decode an encoded string back to its original form by repeating the encoded string 'count' times.
• Parse the input string to extract the count and the encoded string within the brackets

• Use recursion to decode the encoded string by repeating it 'count' times

• Handle nested encoded strings by recursively decoding them

• Output the decoded string for each test case
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Q2. 
Detect and Remove Loop in Linked List
For a given singly linked list, identify if a loop exists and remove it, adjusting the linked list in place. Return the modified linked list.
Expected Complexity:
A...read more
Ans. 
Detect and remove loop in a singly linked list in place with O(n) time complexity and O(1) space complexity.
• Use Floyd's Cycle Detection Algorithm to identify the loop in the linked list.

• Once the loop is detected, use two pointers approach to find the start of the loop.

• Adjust the pointers to remove the loop and return the modified linked list.

• Example: For input 5 2 and 1 2 3 4 5, output should be 1 2 3 4 5.
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Q3. 
Infix to Postfix Conversion
You are provided with a string EXP which represents a valid infix expression. Your task is to convert this given infix expression into a postfix expression.
Explanation:
An i...read more
Ans. 
Convert a given infix expression to postfix expression.
• Use a stack to keep track of operators and operands.

• Follow the rules of precedence for operators (*, / have higher precedence than +, -).

• Handle parentheses by pushing them onto the stack and popping when closing parenthesis is encountered.
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Round duration - 30 minutes
Round difficulty - Medium

Due to pandemic placement process went virtual. Test was conducted at 2 P.M.

Q1. 
Find First Repeated Character in a String
Given a string 'STR' composed of lowercase English letters, identify the character that repeats first in terms of its initial occurrence.
Example:
Input:
STR =...read more
Ans. 
The task is to find the first repeated character in a given string of lowercase English letters.
• Iterate through the string and keep track of characters seen so far in a set.

• If a character is already in the set, return it as the first repeated character.

• If no repeated character is found, return '%'.
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Round duration - 45 minutes
Round difficulty - Medium

Video Call interview where the interview happened for around 45 minutes.

Q1. 
Maximum Sum Path in a Binary Tree Problem Statement
You are provided with a binary tree consisting of N nodes where each node has an integer value. The task is to determine the maximum sum achievable by a...read more
Ans. 
Find the maximum sum achievable by a simple path between any two nodes in a binary tree.
• Traverse the binary tree to find all possible paths and calculate their sums.

• Keep track of the maximum sum encountered during traversal.

• Consider paths that may include the same node twice.

• Implement a recursive function to explore all paths in the tree.

• Optimize the solution to avoid redundant calculations.
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Round duration - 30 minutes
Round difficulty - Easy

Video Call interview where the interview happened for around 30 minutes.

Q1. Api optimisations, query optimisations, how to keep code more extensible, scalable etc
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Q1. Questions related to designing around redis
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Q1. DSA Questions - Easy to medium
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Q1. Hr asked questions About myself
Ans. About last work experience
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Q2. Salary discussion
Ans. Fixed salary amount
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