American Express Software Engineer III Interview Questions and Answers

LinkedList, Stack questions were asked , Deteck loop , Balanced Parenthesis

Q1. Singleton design pattern
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Q2. Collections framework
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Q1. Dont waste time on this one
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Q2. Waste of time, evident from company reviews
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Medium leetcode question on array list

Q1. Core java and collections, exceptions and threading
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Q2. Core java collections
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Q3. Multi threading
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Q4. Executor framework
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Q1. Threading related questions
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They posed questions assessing logical and analytical aptitude.

After completing and passing the aptitude round, I was allowed to take the coding round exam, where the questions ranged from easy to medium level.

Q1. Basic concepts of oops in java. DBMS questions.
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Q2. Questions related to my projects not in dept.
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Q3. They asked me to implement a stack using queues.
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Some questions that range from easy to medium level.

Q1. General questions around your resume, the tech stacks you worked on, fundamentals and deepdive into that.
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Q2. High level system design
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Q1. Can you describe your experience, the projects you have worked on, challenges you solved and other stuffs around that.
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Q1. Salary discussion
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Test was for Web Development - React
75min test
3 Questions
1 Coding Question
2 Scenario based questions

Q1. React Optimization techniques
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Q2. React Advantages
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Q1. How to debug in production environment?
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Q1. Challenges faced during work and how you overcome?
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Q1. Why you choose Wells fargo over other offers?
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1 coding question based on DP for 25 minutes and 30 MCQs on Java , OOPS and code snippet questions also some basic questions based on trees like number of leaf nodes in a complete binary tree with n nodes.

Q1. Write code for finding palindrome of a string
Ans. 
Code to find palindrome of a string
• Iterate through the string from both ends and compare characters

• Use two pointers, one starting from the beginning and one from the end

• If characters at both pointers match, continue checking until they meet in the middle

• If all characters match, the string is a palindrome
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Q2. What is dynamic memory allocation in Java
Ans. 
Dynamic memory allocation in Java refers to the process of allocating memory for objects at runtime.
• Dynamic memory allocation allows for objects to be created and destroyed during program execution.

• The 'new' keyword is used to dynamically allocate memory for objects in Java.

• Dynamic memory allocation helps in managing memory efficiently by allocating memory only when needed.

• Example: int[] arr = new int[5]; dynamically a
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Q3. You are designing an e commerce website which database will you choose and what will you use for authentication given that you can't use JWT or even third party like Google authentication
Ans. 
I would choose a relational database like MySQL and implement a custom authentication system using session management.
• Choose a relational database like MySQL for storing user data, product information, and orders.

• Implement a custom authentication system using session management to securely authenticate users without JWT or third-party services.

• Use encryption techniques to store and validate user passwords securely.

• Util...read more
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Q1. Find the character with the maximum frequency
Ans. 
Iterate through each character in the array of strings and keep track of the frequency of each character. Return the character with the maximum frequency.
• Create a dictionary to store the frequency of each character

• Iterate through each string in the array and then through each character in the string

• Update the frequency count of each character in the dictionary

• Return the character with the maximum frequency
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Q2. Valid parenthesis
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Q1. Have you used Junit? What is the difference between SQl and NoSQl Databases? have you worked with Kafka? Kafka based questions. explain dockerization/ containerization. which java8 feature did you work wit...read more
Ans. 
Yes, I have experience with Junit, SQL and NoSQL databases, Kafka, Dockerization, Java 8 features, stream() operations, and shell scripting in Unix.
• I have used Junit for unit testing in Java projects.

• SQL databases are relational databases that use structured query language for data manipulation, while NoSQL databases are non-relational databases that provide flexible schema design and horizontal scalability.

• I have work...read more
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Q1. What is the most complex sql query you have written till date. Why did you use nested query to achieve your goal? explain the query. which join did you use in the query. have you implemented hashset? how w...read more
Ans. 
The most complex SQL query involved nested queries for data manipulation. Used inner join. Implemented hashset and avoided trees due to their drawbacks.
• Nested SQL query used for complex data manipulation

• Inner join used for combining data from multiple tables

• Implemented hashset for efficient data storage and retrieval

• Avoided trees due to their drawbacks such as unbalanced structure and slower traversal times
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Q2. Find and replace words in a file using shell scripting. add an index in the beginning of each line in a file using shell scripting. what is multithreading? difference between single threaded and multithrea...read more
Ans. 
Shell scripting for find and replace, adding index to lines, multithreading, hashmap vs hashtable, stack vs queue
• Use sed command for find and replace in shell scripting

• Use awk command to add an index at the beginning of each line in a file

• Multithreading is the ability of a CPU to execute multiple threads concurrently

• Single threaded means only one thread is executed at a time, while multithreaded allows multiple threads...read more
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Q1. Behavioral questions- tell me about yourself. do you have any questions for us?
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