10+ American Express Software Developer Interview Questions and Answers

Find the maximum sum of a subsequence without choosing adjacent elements in an array.

• Use dynamic programming to keep track of the maximum sum at each index, considering whether to include or exclude the current element.

• At each index, the maximum sum can be either the sum of the current element and the element two positions back, or the sum at the previous index.

• Iterate through the array and update the maximum sum accordingly.

• Example: For input [3, 2, 7, 10], the maximum non-a...read more

Given a list of strings, determine if a target string can be formed by combining one or more strings from the list.

• Iterate through all possible combinations of strings from the list to form the target string.

• Use recursion to try different combinations of strings.

• Check if the current combination forms the target string.

• Return true if a valid combination is found, otherwise return false.

Determine if all paths from a source node lead to a destination node in a directed graph.

• Check if there is at least one path from source to destination.

• If a node has no outgoing edges, it should be the destination.

• Ensure the number of paths from source to destination is finite.

• Traverse the graph to validate all paths lead to the destination.

Given a string STR and a non-empty string PTR, find all starting indices of anagrams of PTR within STR.

• Create a frequency map of characters in PTR.

• Use sliding window technique to check anagrams in STR.

• Return the starting indices of anagrams found.

The task is to correct a Binary Search Tree by swapping two nodes in the tree.

• Parse the input level order tree and construct the BST

• Identify the two nodes that are swapped incorrectly

• Swap the values of the incorrectly swapped nodes to correct the BST

• Return the corrected BST in level order form

Find maximum sum of disjoint pairs with absolute difference less than K in an array.

• Iterate through the array and sort it.

• Find all possible disjoint pairs with absolute difference less than K.

• Calculate the sum of these pairs to get the maximum sum.

A loop in a linked list can be detected using Floyd's Cycle Detection Algorithm.

• Use two pointers - slow and fast, where slow moves one step at a time and fast moves two steps at a time.

• If there is a loop, the two pointers will eventually meet at some point within the loop.

• To detect the start of the loop, reset one pointer to the head and move both pointers one step at a time until they meet again.

Use streams to find prime numbers in an array

• Use Java streams to filter out non-prime numbers from the array

• Check if a number is prime by dividing it by all numbers less than its square root

• Create a method to check if a number is prime

I leverage Spring Java for dependency injection, MVC framework, and transaction management in my projects.

• Utilize Spring's dependency injection to manage object dependencies and improve code maintainability

• Leverage Spring MVC framework for building web applications with clean separation of concerns

• Use Spring's transaction management to ensure data integrity and consistency in database operations

Implement security in microservices by using authentication, authorization, encryption, and monitoring.

• Use authentication mechanisms like OAuth, JWT, or API keys to verify the identity of clients accessing the microservices.

• Implement authorization controls to define what actions users can perform within the microservices.

• Encrypt data in transit and at rest using protocols like HTTPS and TLS, and tools like Vault or AWS KMS.

• Implement monitoring and logging to detect and respon...read more