'Coding has over 700 languages', '67% of programming jobs aren’t in the technology industry', 'Coding is behind almost everything that is powered by electricity'
American Express interview experience Real time questions & tips from candidates to crack your interview
SDE - Intern
American Express
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4 rounds | 10 Coding problems
Interview preparation journey
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Preparation
Duration: 6 months
Topics: Data Structures, Algorithms, Operating System, DBMS, Dynamic Programming, Backtracking
Tip
Tip

Tip 1 : Do practice a lot of data structures from renowned websites like LeetCode and also from CodeZen
Tip 2 : In your introduction, when asked, you just need to tell your life story.
Tip 3 : Maintain eye contact with the interviewers and clarify every details about the question before proceeding to the solution

Application process
Where: Campus
Eligibility: 7 CGPA
Resume Tip
Resume tip

Tip 1: Add most recent and relevant projects only
Tip 2: you should know each and everything written on your resume

Interview rounds
01
Round
Easy
Online Coding Interview
Duration120 minutes
Interview date29 Aug 2020
Coding problem3

It consisted of 3 coding questions which were purely based on Data Structures and Algorithms.

Question 1 - Find the length of the longest switching sub-array. An array is called switching if all numbers in even positions are equal and all numbers in odd positions are equal. 


Question 2 - It was a long passage question on Dynamic Programming but the solution was really easy.

Question 3 - Given a string S consisting of N lowercase letters, return the minimum number of letters that must be deleted to obtain a word in which every letter occurs a unique number of times. Ex - "aaaabbbb" should return 1, as when we delete 1 a or 1 b , a and b will have different frequencies.


The major point to note in the coding round was that they did not have any time or space limit, so brute force solutions were also accepted. 
The result of my test was declared just as the test ended and I scored a 100%, but they took a long time to release the final shortlist. There was a gap of about a week between the test and interviews.

1. Find the length of the longest switching sub-array. An array is called switching if all numbers in even positions are equal and all numbers in odd positions are equal.
Easy
15m average time
90% success
0/40
Asked in companies
OlaAmerican ExpressTata Consultancy Services (TCS)

You are given an array 'ARR' of 'N' positive integers. You need to find the length of the longest switching contiguous subarray.

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Problem approach

It's like a sliding window problem.
We keep track of even and odd equality with 2 variables, even and odd.
Whenever we come across a unmet condition, like index even but not equal with even variable and same goes for odd, we first
Record the length till now in max_len.
Reset start to i-1 as this is need incase of all elements equal.
Reset even and odd according to current index i...

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2. Chips at Casino

Given two integer N and K representing number of chips a person has and the number of chips he can use at max at a time, return the minimum number of rounds that are necessary for John to leave the casino with N chips, having placed all-in no more than K times. If the person bets C chips and wins he gets 2C chips back and if he loses he doesn't get anything.

Problem approach

It was a dynamic programming question but I was able to solve it with recursion as well.
The approach was simply, that if he wins then he gets 2C chips back. that means 1 turn is used to deploy half the chips he had. while in the other case he just loses a chip and same number of turns are restored.

3. Given a string S consisting of N lowercase letters, return the minimum number of letters that must be deleted to obtain a word in which every letter occurs a unique number of times.For Ex - "aaaabbbb" should return 1, as when we delete 1 a or 1 b , a and b will have different frequencies.
Moderate
15m average time
80% success
0/80
Asked in companies
GooglePaypalAmazon

You are given a string ‘STR’. You need to find and return the minimum number of characters to be deleted from ‘STR’ so that the frequency of each character in the string becomes unique.

Ex...
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02
Round
Easy
HR Round
Duration40 minutes
Interview date5 Sep 2020
Coding problem1

Amex came for two profiles - Tech Role and Analyst, 19 and 23 people respectively were shortlisted for the interviews. Fortunately, I was shortlisted for both the roles. I was asked basic question of C++ and it was majorly an HR Round

1.
Problem approach

Tip 1: Be confident answer honestly as they can catch you easily
Tip 2: Know everything on your resume
Tip 3: Be gentle as you speak

03
Round
Easy
Telephonic
Duration20 minutes
Interview date5 Sep 2020
Coding problem4

It was a fairly simple round conssting of 5 - 6 questions related to coding, puzzles and me.

What are your interests? 
What projects have you done and your field of interest?

1. Q1. How many stacks are used to implement a queue.
Problem approach

Just the answer which is 2.

2. Q2. What is the difference between a reference and a pointer? Explain with an example.
Problem approach

Reference - No memory is allocated and it is just an alias of the same memory location
Pointer - New memory location is created which stores the address of the location it is pointing to.
Ex -
int& a = b (reference)
int* a = &b (pointer)

3. There is a bulb in a room, you are outside the room and there are 3 switches, what is the minimum number of times you need to open the door to know to which switch the bulb belongs
Problem approach

Answer = 1

4. You are given a number if the number is positive, then if n is divisible by 3, print “GO” if n is divisible by 5, print “SLEEP” , if n is divisible by both 3 and 5, print “RETIRE”. If the number equals 0, then throw an exception and print that you have entered 0. If the number is negative, then throw an exception and print that you have entered a negative number.
Problem approach

The question explains everything. Just need to use try catch blocks for exception handling

04
Round
Easy
Face to Face
Duration50 minutes
Interview date5 Sep 2020
Coding problem2

This round was purely technical
No introduction was done, straight to the point

My preference was the Tech Role, so as I was selected in this, I never had to give interviews for the Analyst role. In total 5 people were selected in the Analyst profile and 4 in the Tech profile.

In the end, I was offered a 6 months internship at Amex.

1. Given a linked list of characters, tell if it is a palindrome linked list or not.
Easy
20m average time
90% success
0/40
Asked in companies
HSBCThought WorksPaytm (One97 Communications Limited)

You are given a singly Linked List of integers. Your task is to return true if the given singly linked list is a palindrome otherwise returns false.

For example:
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Problem approach

I gave the two pointer approach. Then he said what if we are provided with the length of the list. I said that we will move forward in the list till n/2 nodes and then the same approach as above. Then he said what if we had to do it with a stack. I said we will add elements into the stack till n/2 nodes and then start popping elements while simultaneously traversing the linked list from the (n/...

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2. You are given a student table and a course table with primary keys -> roll number and course_id in each respectively. Since we know that a student can enroll in many courses and a course can be taken by many students, so how will you establish normalization here in many to many relationships.
Problem approach

We will create a third table that will store only two columns which are the Primary Keys of both the tables and they together can uniquely identify records in both the tables.

I thought of it but did not reach the solution at once, it took me 3 – 4 attempts for it but he didn’t tell me anything, and finally, I got to the solution.

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