American Express Engineer Interview Questions and Answers

Round duration - 90 minutes
Round difficulty - Medium

It was conducted in Hacker rank which consisted of 10 aptitude questions that included C, C++, Java MCQ. 2 programming questions were also given.

Q1. 
Minimum Cost Path Problem Statement
Given an N x M matrix filled with integers, determine the minimum sum obtainable from a path that starts at a specified cell (x, y) and ends at the top left corner of t...read more
Ans. 
The problem involves finding the minimum sum path from a specified cell to the top left corner of a matrix.
• Start from the specified cell and calculate the minimum sum path to reach the top left corner using dynamic programming.

• Consider the three possible moves: down, right, and down-right diagonal.

• Keep track of the minimum sum at each cell and update it based on the minimum of the three possible moves.

• Finally, the mini...read more
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Q2. 
Balanced Parentheses Combinations
Given an integer N representing the number of pairs of parentheses, find all the possible combinations of balanced parentheses using the given number of pairs.
Explanati...read more
Ans. 
Generate all possible combinations of balanced parentheses for a given number of pairs.
• Use backtracking to generate all possible combinations of balanced parentheses.

• Keep track of the number of open and close parentheses used in each combination.

• Recursively generate combinations by adding open parentheses if there are remaining, and closing parentheses if the number of open parentheses is greater than the number of clo...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical round with questions based on data structures, oops and networking.

Q1. 
Character Counting Challenge
Create a program that counts and prints the total number of specific character types from user input. Specifically, you need to count lowercase English alphabets, numeric digi...read more
Ans. 
Create a program to count lowercase alphabets, digits, and white spaces from user input until '$' is encountered.
• Read characters from input stream until '$' is encountered

• Count lowercase alphabets, digits, and white spaces separately

• Print the counts of each character type as three integers separated by spaces
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Q2. 
K Largest Elements Problem Statement
Given an unsorted array containing 'N' integers, you are required to find 'K' largest elements from the array and return them in non-decreasing order.
Input:
The fir...read more
Ans. 
Find K largest elements in an unsorted array and return them in non-decreasing order.
• Sort the array in non-decreasing order.

• Return the last K elements of the sorted array.
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Q3. How can you check whether you have an internet connection on your system?
Ans. 
To check internet connection on a system, you can use various methods like pinging a website or checking network status.
• Use ping command to check connectivity to a website (e.g. ping www.google.com)

• Check network status using network settings or command line tools

• Try accessing a website or online service to verify internet connection
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Q4. What happens when you type a URL in a web browser?
Ans. 
When you type a URL in a web browser, the browser sends a request to the server hosting the website, which then responds with the necessary files to display the webpage.
• Browser checks cache for DNS resolution

• If not found, browser sends a DNS query to resolve the domain name to an IP address

• Browser establishes a TCP connection with the server

• Browser sends an HTTP request to the server for the webpage

• Server processes the...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical round with questions based on data structures, oops and networking.

Q1. 
Counting Sort Problem Statement
Ninja is learning about sorting algorithms, specifically those that do not rely on comparisons. Can you help Ninja implement the counting sort algorithm?
Example:
Input:
...read more
Ans. 
Implement counting sort algorithm to sort an array of integers without comparisons.
• Count the frequency of each element in the input array.

• Calculate the prefix sum of frequencies to determine the position of each element in the sorted array.

• Place each element in its correct position based on the prefix sum.

• Time complexity of counting sort is O(n+k), where n is the number of elements and k is the range of input.

• Example: ...read more
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Q2. What are the applications of the Fibonacci series in real life?
Ans. 
The Fibonacci series has applications in various fields such as mathematics, computer science, art, and nature.
• Used in algorithms for optimization problems and dynamic programming.

• Found in nature, such as the arrangement of leaves on a stem, the branching of trees, and the spiral shapes of shells.

• Applied in financial markets for predicting stock prices and analyzing market trends.

• Utilized in art and design for creating
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Round duration - 30 minutes
Round difficulty - Easy

HR round where the interviewer asked questions to know more about me.