American Express SDE-2 Interview Questions and Answers for Freshers

Assignment was given which was to be completed in a weeks time.

Q1. Expected CTC and other basic details
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Q2. Willing to relocate to the company location
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Round duration - 90 minutes
Round difficulty - Easy

There will be 2 coding questions easy to medium based on DP and linkedlist.

Q1. 
Count Ways To Reach The N-th Stair Problem Statement
You are given a number of stairs, N. Starting at the 0th stair, you need to reach the Nth stair. Each time you can either climb one step or two steps. ...read more
Ans. 
The problem involves finding the number of distinct ways to climb to the N-th stair by taking one or two steps at a time.
• Use dynamic programming to solve this problem efficiently.

• The number of ways to reach the N-th stair is the sum of the number of ways to reach the (N-1)th stair and the (N-2)th stair.

• Handle large inputs by taking modulo 10^9+7 of the result.

• Example: For N=3, there are 3 ways to climb to the third sta
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Round duration - 60 minutes
Round difficulty - Easy

the questions will be be based on trees, linked list and stacks and queues, DP

Q1. 
Left View of a Binary Tree
Given a binary tree, your task is to print the left view of the tree. The left view of a binary tree contains the nodes visible when the tree is viewed from the left side.
Inpu...read more
Ans. 
The task is to print the left view of a binary tree, which contains the nodes visible when the tree is viewed from the left side.
• Traverse the tree level by level and keep track of the leftmost node at each level

• Use a queue for level order traversal and a map to store the leftmost nodes

• Print the values of the leftmost nodes stored in the map as the left view of the tree
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Q2. 
Next Greater Element Problem Statement
You are given an array arr of length N. For each element in the array, find the next greater element (NGE) that appears to the right. If there is no such greater ele...read more
Ans. 
The task is to find the next greater element for each element in an array to its right, if no greater element exists, return -1.
• Use a stack to keep track of elements for which the next greater element is not found yet.

• Iterate through the array from right to left and pop elements from the stack until a greater element is found.

• Store the next greater element for each element in a separate array.

• If the stack is empty afte...read more
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Round duration - 60 minutes
Round difficulty - Medium

(DSA, work experience and personal projects)

Q1. 
Problem: Sort an Array of 0s, 1s, and 2s
Given an array/list ARR consisting of integers where each element is either 0, 1, or 2, your task is to sort this array in increasing order.
Input:
The input sta...read more
Ans. 
Sort an array of 0s, 1s, and 2s in increasing order.
• Use a three-pointer approach to partition the array into sections of 0s, 1s, and 2s.

• Iterate through the array and swap elements based on their values to achieve the sorting.

• Time complexity should be O(N) where N is the number of elements in the array.
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Round duration - 60 minutes
Round difficulty - Medium

It started in the afternoon after the lunch.

Q1. You will be given certain conditions for which you need to design a system. Can you explain your approach to low-level system design?
Ans. 
Approach to low-level system design involves understanding requirements, breaking down components, defining interfaces, and optimizing performance.
• Understand the requirements and constraints of the system

• Break down the system into smaller components/modules

• Define clear interfaces between components for communication

• Optimize performance by considering data structures, algorithms, and resource utilization
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Round duration - 25 minutes
Round difficulty - Easy

Once all the rounds were cleared. I was told that i have 1 more round with manager.

Q1. How do you handle critical situations in a workplace?
Ans. 
I remain calm, assess the situation, prioritize tasks, communicate effectively, and collaborate with team members to find a solution.
• Remain calm and composed under pressure

• Assess the situation to understand the root cause

• Prioritize tasks based on urgency and impact

• Communicate effectively with team members and stakeholders

• Collaborate with team members to brainstorm and implement solutions
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Round duration - 50 minutes
Round difficulty - Easy

Problem-solving round in javascript.
Asked me questions of easy to medium level data structures and algorithm.

Q1. 
Similar String Groups Problem Statement
Two strings S1 and S2 are considered similar if either S1 equals S2 or we can swap two letters of S1 at different positions so that it equals S2.
Input:
The first...read more
Ans. 
The problem involves determining the number of similar string groups in a given list of strings based on a specific criteria.
• Iterate through each pair of strings in the list and check if they are similar based on the given criteria.

• Use a hash set to keep track of visited strings to avoid counting duplicates in the same group.

• Consider implementing a function to check if two strings are similar by allowing at most one sw...read more
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Round duration - 50 minutes
Round difficulty - Medium

Javascrip specific questions

Round duration - 50 minutes
Round difficulty - Easy

Focussed on behavioural aptitude

Round duration - 75 minutes
Round difficulty - Medium

There were 2 coding questions. One was easy to medium difficult and other was of medium difficulty.

Q1. 
Sum Queries in a Sorted Array
Given two arrays arr and queries, your task is to determine the sum of all elements in arr that are less than or equal to each element in queries. The array arr is provided i...read more
Ans. 
Find sum of elements in a sorted array less than or equal to each element in queries.
• Iterate through queries and for each query, find the sum of elements in arr less than or equal to the query element.

• Use binary search to efficiently find the index of the last element less than or equal to the query element.

• Keep track of cumulative sum while iterating through arr to avoid recalculating sums.

• Return the list of sums for
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Q2. 
Find K Closest Elements
Given a sorted array 'A' of length 'N', and two integers 'K' and 'X', your task is to find 'K' integers from the array closest to 'X'. If two integers are at the same distance, pre...read more
Ans. 
Given a sorted array, find K integers closest to X, preferring smaller ones in case of same distance.
• Use binary search to find the closest element to X in the array.

• Maintain two pointers to expand around the closest element to find K closest elements.

• Compare distances and values to select the K closest elements, preferring smaller ones if distances are equal.
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Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
Reverse Only Letters Problem Statement
You are given a string S. The task is to reverse the letters of the string while keeping non-alphabet characters in their original position.
Example:
Input:
S = "...read more
Ans. 
Reverse the letters of a string while keeping non-alphabet characters in their original position.
• Iterate through the string and store the non-alphabet characters in their original positions.

• Reverse the letters of the string using two pointers approach.

• Combine the reversed letters with the non-alphabet characters to get the final reversed string.
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Q2. 
Find The Sum Of The Left Leaves Problem Statement
Given a binary tree with ‘root’, your task is to find and return the sum of all the left leaf nodes.
Example:
Input:
1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1...read more
Ans. 
Find and return the sum of all the left leaf nodes in a binary tree.
• Traverse the binary tree using depth-first search (DFS)

• Check if a node is a leaf node and a left child

• Sum up the values of all left leaf nodes
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Round duration - 60 Minutes
Round difficulty - Easy

Questions related to Java, OOPs, SQL etc. 

Round duration - 60 Minutes
Round difficulty - Easy

It was an HR round.Questions related to resume, Low level design, work experience, behavioural etc. This round stretched more than scheduled time so another round was scheduled which was again a DSA based technical round.

Round duration - 60 Minutes
Round difficulty - Medium

This round had 3 problems. easy, medium and hard.

Q1. 
Median of Two Sorted Arrays
Given two sorted arrays A and B of sizes N and M, find the median of the merged array formed by combining arrays A and B. If the total number of elements, N + M, is even, the m...read more
Ans. 
Find the median of two sorted arrays by merging them and calculating the median of the combined array.
• Merge the two sorted arrays into one sorted array.

• Calculate the median of the combined array based on the total number of elements.

• Return the median as the result.
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Q2. 
Palindrome Checker Problem Statement
Given an alphabetical string S, determine whether it is a palindrome or not. A palindrome is a string that reads the same backward as forward.
Input:
The first line ...read more
Ans. 
Check if a given string is a palindrome or not.
• Iterate through the string from both ends and compare characters.

• If all characters match, return 1 indicating a palindrome.

• If any characters don't match, return 0 indicating not a palindrome.
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Q3. 
Minimum Character Deletion Problem Statement
You have been provided a string STR. Your task is to find and return the minimum number of characters that need to be deleted from STR so that each character's...read more
Ans. 
Find the minimum number of character deletions needed to make each character's frequency unique in a given string.
• Iterate through the string and count the frequency of each character.

• Identify characters with the same frequency and calculate the minimum deletions needed to make them unique.

• Return the total minimum deletions for each test case.
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Had questions on graph

Q1. Binary Search leftmost rightmost
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Q1. Monotonic stack question
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Q1. System design round, discussed subscriber publisher design pattern
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Round duration - 80 minutes
Round difficulty - Medium

Q1. 
Longest Increasing Path in Matrix Problem Statement
Given a 2-D matrix mat with 'N' rows and 'M' columns, where each element at position (i, j) is mat[i][j], determine the length of the longest increasing...read more
Ans. 
The problem involves finding the length of the longest increasing path in a 2-D matrix starting from a given cell.
• Use dynamic programming to keep track of the longest increasing path starting from each cell.

• Implement a recursive function to explore all possible paths from a cell.

• Update the length of the longest path for each cell based on the maximum path length from its neighbors.

• Consider edge cases such as boundary c...read more
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Round duration - 50 minutes
Round difficulty - Hard

It was purely Data Structures and Maths.

Q1. 
Arithmetic Progression Queries Problem Statement
Given an integer array ARR of size N, perform the following operations:
- update(l, r, val): Add (val + i) to arr[l + i] for all 0 ≤ i ≤ r - l.
- rangeSu...read more
Ans. 
Implement update and rangeSum operations on an integer array based on given queries.
• Implement update(l, r, val) by adding (val + i) to arr[l + i] for all i in range (0, r - l).

• Implement rangeSum(l, r) to return the sum of elements in the array from index l to r.

• Handle queries using 1-based indexing.

• Ensure constraints are met for input values.

• Output the sum of arr[l..r] for each rangeSum operation.
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Round duration - 70 Minutes
Round difficulty - Easy

Round duration - 30 Minutes
Round difficulty - Easy

Q1. 
Pattern Matching Problem Statement
Given a pattern as a string and a set of words, determine if the pattern and the words list align in the same sequence.
Input:
T (number of test cases)
For each test ca...read more
Ans. 
The problem involves determining if a given pattern aligns with a list of words in the same sequence.
• Iterate through the pattern and words list simultaneously to check for matching sequences.

• Use a hashmap to store the mapping between characters in the pattern and words in the list.

• Compare the mappings to determine if the pattern and words align in the same sequence.
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DSA, Leetcode medium -2 problems

Q1. Easy Leetcode Problem: Count of substrings with no repeating characters
Ans. 
Count substrings with unique characters in a given string
• Use a sliding window approach to keep track of unique characters in a substring

• Use a set to store characters in the current window and update the window accordingly

• Increment the count of valid substrings whenever a new character is added to the set
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Q2. Debugging a Java Code
Ans. 
Debugging a Java code involves identifying and fixing errors in the code to ensure it runs correctly.
• Start by understanding the error message or symptoms of the issue.

• Use debugging tools like breakpoints, watches, and logging to track the flow of the code.

• Review the code logic and check for common mistakes like typos, incorrect variable assignments, or logic errors.

• Test different scenarios to reproduce the issue and na...read more
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Q1. Design Parking System
Ans. 
Design a parking system with different types of parking spots
• Create classes for different types of parking spots (e.g. compact, regular, handicap)

• Implement methods for checking availability, reserving, and releasing spots

• Consider implementing a parking lot class to manage all parking spots
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