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# American Express EDA/CFR | On-Campus for Internship

• Difficulty Level : Expert
• Last Updated : 11 Sep, 2021

### Round 1: Technical and Aptitude Assessment

1. MCQs based on
• Aptitude
• Output-based
• SQL
2. Two simple coding questions.

### Round 2: Technical Interview

1. Given a list [1, 2, 3, 1, 2, 3, 4, 5, 5, 8, 1]. Write code in python to convert this list to a dictionary where the elements of the dictionary should be stored with their frequencies.
2. Write the code for the same question in Java/C/C++. Article link. Problem Link
3. What is the difference between tuple, list, and array?
4. Amex has many swipe machines. And each swipe machine has an ID given to a particular brand at a particular point of time. Given two tables:
1. Table 1: ID, Brand, Date of start,   Date of expiry
2. Table 2: ID, Brand, Transaction ID
3. Write an SQL query to accumulate all the transactions for each brand whenever it had that particular machine.
5. Explain the K-Nearest Neighbors algorithm.
6. Explain Decision Tree.
7. Discussions on projects mentioned in resume.
8. How KNN used in sentiment analysis?
9. Approach to count the number of cars in a particular state? (Hint: Sample of a population)
10. For Amex’s swipe machines, how can it be alerted if any of their machines stop working before the user of the machine complains?

### Round 3: Technical Interview

1. Hourglass puzzle
2. If there are three lamps in a room and their switches are outside the room. The room is completely closed. How can we know which switch is connected to which bulb? (Hint: Heat)
3. There are 3 boxes. The first box has all white balls, the second box has all black balls and the third one has a mixture of both white and black balls. There are tags on each of the boxes but none of the tags is correct. Identify the correct tags.

### Round 4: Technical HR Interview

1. Introduce yourself.
2. Project-specific questions.
3. A cube is painted with red color. This cube is cut 2 times horizontally and 2 times vertically. What is the probability that when all the cubes are thrown and all have a painted face on top?