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10+ American Express Software Developer Intern Interview Questions and Answers

Updated 5 Feb 2024

Q1. Unique Frequency Problem Statement

Given a string 'STR' with lowercase letters, determine the minimum number of deletions required to ensure that every letter in the string appears a unique number of times.

Exa...read more

Ans.

The task is to find the minimum number of deletions needed in a string to ensure each character appears a unique number of times.

  • Iterate through the string and count the frequency of each character

  • Track the frequencies in a hashmap

  • Identify the characters with duplicate frequencies and calculate the minimum deletions needed

  • Return the minimum number of deletions for each test case

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Q2. Longest Switching Subarray Problem Statement

Determine the length of the longest contiguous subarray in a given array of positive integers, where the subarray qualifies as 'switching'. An array is defined as sw...read more

Ans.

Find the length of the longest switching subarray in a given array of positive integers.

  • Iterate through the array and keep track of the longest switching subarray found so far.

  • Check if the numbers at even and odd positions are identical to determine a switching subarray.

  • Return the length of the longest switching subarray.

  • Example: For input [1, 4, 1, 4, 3, 2, 3, 0], the longest switching subarray is [1, 4, 1, 4] with length 4.

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American Express Software Developer Intern Interview Questions and Answers for Freshers
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Q3. Palindrome Linked List Detection

Given a singly linked list of integers, determine if it is a palindrome. A linked list is considered a palindrome if it reads the same forward and backward.

Example:

Input:
The ...read more
Ans.

Check if a singly linked list is a palindrome by comparing elements from both ends.

  • Traverse the linked list to find the middle point

  • Reverse the second half of the linked list

  • Compare the first half with the reversed second half to check for palindrome

  • Example: Input: 1 2 3 2 1 -1, Output: true

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Q4. Travelling Salesman Problem

Given a list of cities numbered from 0 to N-1 and a matrix DISTANCE consisting of 'N' rows and 'N' columns, representing the distances between each pair of cities, find the shortest ...read more

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Q5. Sliding Maximum Problem Statement

Given an array of integers ARR of length 'N' and a positive integer 'K', find the maximum elements for each contiguous subarray of size K.

Example:

Input:
ARR = [3, 4, -1, 1, 5...read more
Ans.

Implement a function to find maximum elements for each contiguous subarray of size K in an array of integers.

  • Iterate through the array and maintain a deque to store the indices of elements in decreasing order.

  • Pop elements from the deque that are out of the current window and add the maximum element to the result array.

  • Return the result array containing maximum elements for each subarray of size K.

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Q6. Longest Substring with At Most K Distinct Characters

Given a string S of length N and an integer K, find the length of the longest substring that contains at most K distinct characters.

Input:

The first line co...read more
Ans.

Find the length of the longest substring with at most K distinct characters in a given string.

  • Use a sliding window approach to keep track of the characters and their counts in the substring.

  • Maintain a hashmap to store the characters and their frequencies within the window.

  • Update the window size and characters count as you iterate through the string.

  • Keep track of the longest substring length with at most K distinct characters.

  • Return the length of the longest substring for each...read more

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Q7. Interval List Intersection Problem

You are provided with two sorted lists of closed intervals, INTERVAL1 and INTERVAL2. A closed interval [x, y] (x < y) signifies the set of real numbers z such that x <= z <= y...read more

Ans.

Find the intersections of two sorted lists of closed intervals.

  • Iterate through both interval lists to find intersections

  • Compare the intervals and find the common range

  • Handle cases where there is no intersection between intervals

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Q8. Stack using Two Queues Problem Statement

Develop a Stack Data Structure to store integer values using two Queues internally.

Your stack implementation should provide these public functions:

Explanation:

1. Cons...read more
Ans.

Implement a stack using two queues to store integer values with specified functions.

  • Use two queues to simulate stack operations efficiently.

  • Maintain one queue for storing elements and another for temporary storage during push operation.

  • Ensure proper handling of edge cases like empty stack or invalid operations.

  • Example: Push operation involves transferring elements from one queue to another before adding the new element.

  • Example: Pop operation removes and returns the top elemen...read more

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Q9. Detect and Remove Loop in Linked List

For a given singly linked list, identify if a loop exists and remove it, adjusting the linked list in place. Return the modified linked list.

Expected Complexity:

Aim for a...read more

Ans.

Detect and remove loop in a singly linked list in place with O(n) time complexity and O(1) space complexity.

  • Use Floyd's Cycle Detection Algorithm to identify the loop in the linked list.

  • Once the loop is detected, use two pointers to find the start of the loop.

  • Adjust the pointers to remove the loop and return the modified linked list.

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Q10. Minimum Number of Swaps to Sort an Array

Find the minimum number of swaps required to sort a given array of distinct elements in ascending order.

Input:

T (number of test cases)
For each test case:
N (size of the...read more
Ans.

The minimum number of swaps required to sort a given array of distinct elements in ascending order.

  • Use a graph-based approach to find cycles in the array

  • Count the number of swaps needed to fix each cycle

  • Sum up the swaps needed for all cycles to get the total minimum swaps

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Q11. Maximum Non-Adjacent Subsequence Sum

Given an array of integers, determine the maximum sum of a subsequence without choosing adjacent elements in the original array.

Input:

The first line consists of an integer...read more
Ans.

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 is either the sum of the current element and the sum 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-adjacent ...read more

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Q12. Left View of a Binary Tree Problem Statement

Given a binary tree, your task is to print the left view of the tree.

Example:

Input:
The input will be in level order form, with node values separated by a space. U...read more
Ans.

Print the left view of a binary tree given in level order form.

  • Traverse the tree level by level and print the first node encountered at each level

  • Use a queue to perform level order traversal

  • Keep track of the current level and the maximum level seen so far

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