Amazon Software Developer Intern Interview Questions, Process, and Tips

Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Search in a Row-wise and Column-wise Sorted Matrix Problem Statement
You are given an N * N matrix of integers where each row and each column is sorted in increasing order. Your task is to find the positi...read more
Ans. 
Given a sorted N * N matrix, find the position of a target integer X within the matrix.
• Iterate over each row and column to search for the target integer X.

• Utilize the sorted nature of the matrix to optimize the search process.

• Return the position of X if found, otherwise return -1 -1.
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Q2. 
Count Pairs with Given Sum
Given an integer array/list arr and an integer 'Sum', determine the total number of unique pairs in the array whose elements sum up to the given 'Sum'.
Input:
The first line c...read more
Ans. 
Count the total number of unique pairs in an array whose elements sum up to a given value.
• Use a hashmap to store the frequency of each element in the array.

• Iterate through the array and for each element, check if (Sum - current element) exists in the hashmap.

• Increment the count of pairs if the complement exists in the hashmap.
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Fire in the Cells Problem Statement
Given a matrix MAT of size N * M, where each cell is either on fire or safe, determine if a person can reach an escape cell without being burnt. The person starts from ...read more
Ans. 
Determine if a person can reach an escape cell without encountering fire in a given matrix.
• Check if the person can reach an escape cell without encountering fire by simulating the movement of the person and fire spread.

• If the person can reach an escape cell, return the time taken; otherwise, return -1.

• Consider the constraints and edge cases while implementing the solution.
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Add Two Numbers Represented by Linked Lists
Your task is to find the sum list of two numbers represented by linked lists and return the head of the sum list.
Explanation:
The sum list should be a linked...read more
Ans. 
Add two numbers represented by linked lists and return the head of the sum list.
• Traverse both linked lists simultaneously while keeping track of carry from previous sum

• Create a new linked list to store the sum of the two numbers

• Handle cases where one linked list is longer than the other by padding with zeros

• Update the sum and carry at each node while iterating through the linked lists
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Q2. 
Check If Linked List Is Palindrome
Given a singly linked list of integers, determine if the linked list is a palindrome.
Explanation:
A linked list is considered a palindrome if it reads the same forwar...read more
Ans. 
Check if a given singly linked list of integers is a palindrome or not.
• Traverse the linked list to find the middle element using slow and fast pointers.

• Reverse the second half of the linked list.

• Compare the first half with the reversed second half to determine if it's a palindrome.
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Square Root with Decimal Precision Problem Statement
You are provided with two integers, 'N' and 'D'. Your objective is to determine the square root of the number 'N' with a precision up to 'D' decimal pl...read more
Ans. 
Implement a function to find the square root of a number with a given precision up to a specified number of decimal places.
• Implement a function that takes two integers N and D as input and returns the square root of N with precision up to D decimal places.

• Use mathematical algorithms like Newton's method or binary search to approximate the square root with the desired precision.

• Ensure that the difference between the com...read more
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Q2. 
Alien Dictionary Problem Statement
You are provided with a sorted dictionary (by lexical order) in an alien language. Your task is to determine the character order of the alien language from this dictiona...read more
Ans. 
Given a sorted alien dictionary in an array of strings, determine the character order of the alien language.
• Iterate through the dictionary to build a graph of character dependencies.

• Perform a topological sort on the graph to determine the character order.

• Return the character array representing the order of characters in the alien language.
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Round duration - 50 Minutes
Round difficulty - Medium

Q1. 
Maximal AND Subsequences Problem
Given an array consisting of N integers, your task is to determine how many k-element subsequences of the given array exist where the bitwise AND of the subsequence's elem...read more
Ans. 
Find the maximal AND value and count of subsequences in an array.
• Iterate through all possible k-element subsequences and calculate their AND value.

• Track the maximal AND value and count of subsequences achieving this value.

• Return the maximal AND value and count modulo 1000000007.
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Round duration - 50 Minutes
Round difficulty - Easy

Q1. What are semaphores?
Ans. 
Semaphores are synchronization primitives used to control access to shared resources in a multi-threaded environment.
• Semaphores can be used to limit the number of threads accessing a resource simultaneously.

• They can be binary (mutex) or counting semaphores.

• Operations on semaphores include wait (P) and signal (V).

• Example: In a producer-consumer problem, semaphores can be used to control access to a shared buffer.
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Round duration - 50 Minutes
Round difficulty - Easy

Q1. What is virtual memory?
Ans. 
Virtual memory is a memory management technique that allows a computer to compensate for physical memory shortages by temporarily transferring data from RAM to disk storage.
• Virtual memory allows programs to use more memory than is physically available on the system.

• It helps in running multiple programs simultaneously by allocating a portion of the hard drive as additional RAM.

• Virtual memory uses a combination of RAM an...read more
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Check If Linked List Is Palindrome
Given a singly linked list of integers, determine if the linked list is a palindrome.
Explanation:
A linked list is considered a palindrome if it reads the same forwar...read more
Ans. 
Check if a given singly linked list of integers is a palindrome or not.
• Traverse the linked list to find the middle element using slow and fast pointers.

• Reverse the second half of the linked list.

• Compare the first half with the reversed second half to determine if it's a palindrome.
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Q2. 
Total Unique Paths Problem Statement
You are located at point ‘A’, the top-left corner of an M x N matrix, and your target is point ‘B’, the bottom-right corner of the same matrix. Your task is to calcula...read more
Ans. 
Calculate total unique paths from top-left to bottom-right corner of a matrix by moving only right or down.
• Use dynamic programming to solve the problem efficiently.

• Create a 2D array to store the number of unique paths for each cell.

• Initialize the first row and first column with 1 as there is only one way to reach them.

• For each cell (i, j), the number of unique paths is the sum of paths from the cell above and the cell ...read more
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Square Root with Decimal Precision Problem Statement
You are provided with two integers, 'N' and 'D'. Your objective is to determine the square root of the number 'N' with a precision up to 'D' decimal pl...read more
Ans. 
Implement a function to find the square root of a number with a given precision up to a specified number of decimal places.
• Implement a function that takes two integers N and D as input and returns the square root of N with precision up to D decimal places.

• Use mathematical algorithms like Newton's method or binary search to approximate the square root with the desired precision.

• Ensure that the difference between the com...read more
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Q2. Can you explain the ACID properties in the context of database management systems?
Ans. 
ACID properties ensure database transactions are processed reliably and consistently.
• Atomicity: Ensures that either all operations in a transaction are completed successfully or none at all.

• Consistency: Ensures that the database remains in a valid state before and after the transaction.

• Isolation: Ensures that transactions are executed independently and do not interfere with each other.

• Durability: Ensures that once a tr...read more
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Round duration - 60 Minutes
Round difficulty - Easy

3 coding questions and the duration of the test was 90 mins

Q1. 
Merge Two Sorted Linked Lists Problem Statement
You are provided with two sorted linked lists. Your task is to merge them into a single sorted linked list and return the head of the combined linked list.
...read more
Ans. 
Merge two sorted linked lists into a single sorted linked list without using additional space.
• Create a dummy node to start the merged list

• Compare the nodes of both lists and link them accordingly

• Move the pointer to the next node in the merged list

• Handle cases where one list is empty or both lists are empty

• Time complexity: O(n), Space complexity: O(1)
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Q2. 
Rat in a Maze Problem Statement
You need to determine all possible paths for a rat starting at position (0, 0) in a square maze to reach its destination at (N-1, N-1). The maze is represented as an N*N ma...read more
Ans. 
Find all possible paths for a rat in a maze from source to destination.
• Use backtracking to explore all possible paths in the maze.

• Keep track of visited cells to avoid revisiting them.

• Explore all possible directions ('U', 'D', 'L', 'R') from each cell.

• Terminate the search when the destination cell is reached.

• Return the list of valid paths sorted in alphabetical order.
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Q3. 
Find All Pairs Adding Up to Target
Given an array of integers ARR of length N and an integer Target, your task is to return all pairs of elements such that they add up to the Target.
Input:
The first line ...read more
Ans. 
Given an array of integers and a target, find all pairs of elements that add up to the target.
• Iterate through the array and for each element, check if the complement (target - current element) exists in a hash set.

• If the complement exists, add the pair to the result. If not, add the current element to the hash set.

• Handle cases where the same element is used twice in a pair to avoid duplicates.

• Return (-1, -1) if no pair...read more
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Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
Longest Increasing Subsequence Problem Statement
Given an array of integers with 'N' elements, determine the length of the longest subsequence where each element is greater than the previous element. This...read more
Ans. 
Find the length of the longest strictly increasing subsequence in an array of integers.
• Use dynamic programming to keep track of the longest increasing subsequence ending at each element.

• Initialize an array to store the length of the longest increasing subsequence ending at each index.

• Iterate through the array and update the length of the longest increasing subsequence for each element.

• Return the maximum value in the ar...read more
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Q2. 
Boundary Traversal of a Binary Tree
Given a binary tree of integers, your task is to return the boundary nodes of the tree in Anti-Clockwise direction starting from the root node.
Input:
The first line ...read more
Ans. 
Return the boundary nodes of a binary tree in Anti-Clockwise direction starting from the root node.
• Traverse the left boundary nodes in top-down order

• Traverse the leaf nodes from left to right

• Traverse the right boundary nodes in bottom-up order

• Handle cases where duplicates occur in the boundary nodes

• Implement the function without printing as printing is already managed
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Q3. 
Spiral Matrix Problem Statement
You are given a N x M matrix of integers. Your task is to return the spiral path of the matrix elements.
Input
The first line contains an integer 'T' which denotes the nu...read more
Ans. 
The task is to return the spiral path of elements in a given matrix.
• Iterate through the matrix in a spiral path by keeping track of boundaries.

• Print elements in the order of top, right, bottom, and left sides of the matrix.

• Handle cases where the matrix is not a square matrix separately.

• Consider edge cases like single row or single column matrices.
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Round duration - 50 Minutes
Round difficulty - Medium

This was the last round, which consists of some basic hr questions and theory questions.

Round duration - 180 Minutes
Round difficulty - Hard

This was an online technical round on the SHL platform. The link of the test was shared to us around 3 PM. 
There were 4 sections and each section had limited time. You can NOT go back to the question you have already attempted. 
The webCam was not on. 
Section 1: Automata/ Debugging
Section 2: Coding
Section 3: Amazon Principles/Personality Based
Section 4: Aptitude/Verbal

Q1. 
Favourite Operation - Problem Statement
Ninja has studied the bitwise operations ‘AND’ and ‘XOR’. He received an assignment that involves these operations and needs help to complete it efficiently before ...read more
Ans. 
Calculate bitwise 'AND' and 'XOR' of subarrays of size at most K in an array efficiently.
• Iterate through all subarrays of size at most K and calculate bitwise 'AND'.

• Calculate the 'XOR' of all the bitwise 'AND' results to get the final output.

• Optimize the solution to handle large input sizes efficiently.
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Q2. 
Critical Connection Problem Statement
In a network with 'N' system nodes, identified from 0 to N-1, and 'M' connections, determine all critical connections. A connection is critical if its removal disrupt...read more
Ans. 
Implement a function to find critical connections in a network with system nodes and connections.
• Create an adjacency list to represent the network connections.

• Use Tarjan's algorithm to find critical connections in the network.

• Output the count of critical connections and the pairs of nodes involved.

• Handle multiple test cases efficiently.

• Ensure that the removal of a critical connection disrupts network connectivity.
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Round duration - 50 Minutes
Round difficulty - Easy

Time: 9 am to 10 am
Mode of Interview: Amazon Chime Video
LiveCode: To write code, it was not a compiler.
The interviewer was very nice.

Q1. 
Product Of Array Except Self Problem Statement
You are provided with an integer array ARR of size N. You need to return an array PRODUCT such that PRODUCT[i] equals the product of all the elements of ARR ...read more
Ans. 
Return an array of products of all elements in an array except the current element.
• Iterate through the array twice to calculate the product of all elements to the left and right of each element.

• Use two arrays to store the products of elements to the left and right of each element.

• Multiply the corresponding elements from the left and right product arrays to get the final product array.
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Round duration - 50 Minutes
Round difficulty - Medium

Time: 3 pm to 4 pm
Mode of Interview: Amazon Chime Video
LiveCode: To write code, it was not a compiler
The interviewer was time adamant and not very supportive. A shadow interviewer was also there.

Q1. 
LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key) - Return the value of the key if it exists in the cache; otherw...read more
Ans. 
Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.
• Use a combination of a doubly linked list and a hashmap to efficiently implement the LRU cache.

• Maintain a doubly linked list to keep track of the order of keys based on their recent usage.

• Use a hashmap to store key-value pairs for quick access and update operations.

• When a key is accessed or updated, mov...read more
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