Amazon Software Developer Interview Questions, Process, and Tips

Round duration - 90 minutes
Round difficulty - Easy

It consisted of two sections - first section had two coding questions and second section had to submit explanations for your solutions. One of the question was a simple spiral traversal of a two-dimensional matrix. Other was a straightforward binary search question. Level of this round was very easy.

Q1. 
Spiral Matrix Problem Statement
You are provided with a 2-D array called MATRIX with dimensions N x M containing integers. Your task is to return the matrix's elements in a spiral order.
Example:
Inpu...read more
Ans. 
The task is to return the elements of a 2-D array in a spiral order.
• Traverse the matrix in a spiral order by moving right, down, left, and up.

• Keep track of the boundaries of the matrix as you move along.

• Handle cases where the matrix is not a square (N != M).
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Q2. 
Covid Vaccination Distribution Problem
As the Government ramps up vaccination drives to combat the second wave of Covid-19, you are tasked with helping plan an effective vaccination schedule. Your goal is...read more
Ans. 
Given constraints and rules, find maximum vaccines administered on a specific day during a vaccination drive.
• Iterate through each test case and calculate the maximum number of vaccines distributed on the specified day.

• Distribute vaccines evenly across days while maximizing the number on the specified day.

• Ensure that the sum of vaccines distributed does not exceed the maximum allowed.

• Consider edge cases like when the nu...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This was the first F2F interview. He started by asking me about the work I did in my previous company. He seemed genuinely interested in knowing the project I was working on. Also asked me some technical questions related to that project. Asked a couple of questions related to the skills I had mentioned on my resume like AWS lambda etc. I was able to answer all question correctly except one. Then I was given one coding task to solve. I was required to start coding instantly and explain what I was doing simultaneously. Other than the coding task, interviewer asked me a couple of behavioral questions

Q1. What are the differences between static and dynamic memory allocation?
Ans. 
Static memory allocation is done at compile time, while dynamic memory allocation is done at runtime.
• Static memory allocation is fixed in size and allocated on the stack, while dynamic memory allocation can change in size and is allocated on the heap.

• Static memory allocation is determined at compile time, while dynamic memory allocation is determined at runtime.

• Static memory allocation is less flexible but faster, whil...read more
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Round duration - 60 Minutes
Round difficulty - Easy

Asked me two coding questions.

Q1. 
Binary Strings Without Consecutive 1s Problem Statement
Given an integer K, your task is to generate all binary strings of length K such that there are no consecutive 1s in the string.
This means the bin...read more
Ans. 
Generate all binary strings of length K without consecutive 1s in lexicographically increasing order.
• Use backtracking to generate all possible binary strings without consecutive 1s.

• Start with an empty string and recursively add '0' or '1' based on the condition of no consecutive 1s.

• Keep track of the current string and its length to check for consecutive 1s.

• Return the generated binary strings in lexicographically increa
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Round duration - 60 Minutes
Round difficulty - Medium

This was HM round. He asked me some behavioral questions which seemed like a formality. He asked me some questions on OOPS and OS. Then gave me a coding question. Wanted me to explain the approach and run it. I asked him a couple of question at the end of interview related to the work and tech stack used by the team.

Q1. 
Number with Maximum Probability Problem Statement
In this game, players Ninja Misha and Ninja Andrew each choose an integer within the range of 1 to 'N'. After their choices, a random integer 'C' is drawn...read more
Ans. 
Find the optimal number for Andrew to choose to maximize his winning probability in a game against Misha.
• Andrew should choose the number equidistant from Misha's number and the random integer C to maximize his winning probability.

• The optimal number for Andrew to choose is the average of Misha's number and C, rounded up if the average is not an integer.

• If the average of Misha's number and C is an integer, Andrew should ...read more
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Round duration - 60 Minutes
Round difficulty - Medium

He asked me some questions about my role in previous organization. Asked me the architecture of the systems I have worked on. Then asked me a coding question.

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.
• Use binary search on each row to find the potential row where the target might be located.

• Then use binary search on that row to find the column where the target is located.

• Return the position if found, otherwise return -1 -1.
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Round duration - 90 Minutes
Round difficulty - Easy

Online Coding Round

Q1. 
Shortest Path in a Binary Maze
Find the length of the shortest path in a binary maze given in the form of a rectangular matrix of size M*N, where each element is 0 or 1. Calculate the shortest path from a...read more
Ans. 
Step 1 -> Start a BFS from the given source point
Step 2 -> Maintain a counter variable which holds the value of the level of BFS which is being investigated
Step 3-> When you reach the target cell point return the value of counter variable which will denote the shortest distance.
Step 4-> If target is not reached return -1 in the end after the BFS is completed
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Q2. 
Connecting Ropes with Minimum Cost
You are given 'N' ropes, each of varying lengths. The task is to connect all ropes into one single rope. The cost of connecting two ropes is the sum of their lengths. Yo...read more
Ans. 
Step 1 -> Declare a Min Heap and push all the given rope lengths in it.
Step 2 -> Execute till the size of the Min Heap is greater than 2.
Step 3 -> At each step take the top most two entries from the Min Heap and add them to your cost.
Step 4 -> Also add the two min entries taken at some point back to Min heap as two ropes of size x and y when joined together creates a new rope of size x+y which can be used f...read more
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Round duration - 60 minutes
Round difficulty - Medium

Problem Solving and Data Structures round.

Q1. 
Anagram Pairs Verification
In this task, you need to verify if two provided strings are anagrams of each other. Two strings are considered anagrams if you can rearrange the letters of one string to form t...read more
Ans. 
Step 1-> Run two nested for loops to check for each pair (arr[i],arr[j]) are anagrams of each other or not.
Step 2-> For checking anagrams I used hashing where I counted frequency of each character if all the frequencies were same in both the string return true else return false that they are not anagrams.
Step 3 -> Grouped the pairs which matched that they are anagrams.

Extended Problem Solution:
When all the cha...read more
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Q2. 
Inversion Count Problem
Given an integer array ARR of size N with all distinct values, determine the total number of 'Inversions' that exist.
Explanation:
An inversion is a pair of indices (i, j) such t...read more
Ans. 
First I gave a Brute force solution using two nested Loops and trying out all pairs, which Interviewer asked me to optimize.
I asked about the constraints of elements occurring in the array , it was given that each arr[i]<=10^5 
Step 1 -> Declare a Binary Indexed Tree of size equal to maximum element occurring in array 
Step 2- > Traverse array from end till start (N-1 index till 0) and at each step if ...read more
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Round duration - 60 Minutes
Round difficulty - Medium

DSA and Problem Solving

Q1. 
Minimum Window Subsequence Problem Statement
You are given two strings S and T. Your task is to determine the smallest contiguous substring W of S, such that T is a subsequence of W.
A subsequence is a s...read more
Ans. 
Step 1 -> Gave a Brute force solution by trying out all substrings and building a check function to verify if current window has all characters of other string or not.
Step 2-> I was told to optimize it
Step 3-> Tried using hashing + sliding window
Step 4 -> was not able to code it up properly.
Step 5 -> Tried doing it using Binary search where start=Length of String B and end= String length of A and tried e...read more
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Round duration - 75 Minutes
Round difficulty - Easy

Deep discussions about projects about the tech stack used and why it is used . In depth subject questions .

Difficult level medium

Q1. Lru cache using hashmap and doubly linked list
Ans. 
LRU cache can be implemented using a hashmap to store key-value pairs and a doubly linked list to keep track of the most recently used items.
• Use a hashmap to store key-value pairs for quick access to values

• Use a doubly linked list to keep track of the order of items based on their usage

• When a new item is accessed, move it to the front of the linked list and update the hashmap accordingly

• When the cache is full, remove t...read more
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Q1. Hotel bookings possible question from interviewbit
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Questions like leetcode, a lot of double linked lists

Q1. The last time i was failed
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Q2. How i deal with failure
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Round duration - 120 Minutes
Round difficulty - Easy

The round started from 11AM. The test can be given from home from a laptop.

Q1. 
K Closest Points to Origin Problem Statement
Your house is located at the origin (0,0) of a 2-D plane. There are N neighbors living at different points on the plane. Your goal is to visit exactly K neighb...read more
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Round duration - 60 minutes
Round difficulty - Medium

The interview started around 10 AM and it was on the video call.

Q1. 
LCA of Binary Tree Problem Statement
You are given a binary tree consisting of distinct integers and two nodes, X and Y. Your task is to find and return the Lowest Common Ancestor (LCA) of these two nodes...read more
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Q2. 
Word Search Problem Statement
Given a matrix of characters with dimensions N * M, you need to process 'Q' queries. For each query, you are given a word 'W' and you must determine if you can form word 'W' ...read more
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