Amazon Software Developer Intern Interview Questions, Process, and Tips

Round duration - 90 Miinutes
Round difficulty - Medium

The round has 2 sections each.

1) First Section consisted of 2 coding questions.
2) Second Section consisted of 28 multiple choice questions(MCQs)

Q1. Equation Solver
You are given an equation of the addition of two numbers. One number among the two operands is missing in the given equation and is denoted by ‘x’. You have to find this missing number and ...read more
Ans. Solving the equation
• Declare three string variables ‘FIRST_NUMBER’, ‘SECOND_NUMBER’, ‘THIRD_NUMBER’.
• Iterate the string from index 0 till just before the ‘+’ character and store it in variable ‘FIRST_NUMBER’.
• Store the substring starting just after ‘+’ character and ending just before the ‘=’ character in the variable ‘SECOND_NUMBER’.
• Store the substring starting just after ‘=’ character and till the end in variable ‘THIRD...read more
Answered by CodingNinjas
Add your answer
Q2. Anagram Pairs
Pre-requisites: Anagrams are defined as words or names that can be formed by rearranging letters of another word. Such as "spar" can be formed by rearranging letters of "rasp&q...read more
Ans. Count Characters
Anagrams have a unique property: the counts of each distinct character present in both strings are the same. One way to check this is: 
1. Sort both strings, so that all the same characters come together
2. Then loop through both strings together and check each element in both strings one by one
3. If at any position, the characters are found to be different or if the lengths of the two strings are different, ...read more
Answered by CodingNinjas
View 1 more answer

Round duration - 45 Minutes
Round difficulty - Medium

This was my first technical round and the interviewer mainly tested my problem solving skills.

Q1. Minimum steps to reach target by a Knight
You have been given a square chessboard of size ‘N x N’. The position coordinates of the Knight and the position coordinates of the target are also given.
Your t...read more
Ans.  Using BFS
The idea is to perform BFS traversal. Start from the initial position of the Knight and proceed to further cells. Traversal is performed using a queue. The queue stores the different paths travelled by the knight and also keeps storing the count of steps. When the target is popped from the queue, the corresponding count of the steps is the answer.
 
1. Define a class with the following data members
     &nbs...read more
Answered by CodingNinjas
View 1 more answer
Q2. OS Questions
1) Explain about Round Robin Scheduling Algorithm?
2) Asked about paging and virtual memory
3) Explain about thrashing phenomenon
Add your answer

Round duration - 120 minutes
Round difficulty - Easy

This round consisted of two coding questions which were of medium level.

Q1. Minimum Cost to Destination
You have given a m*n matrix filled with "1" and "0"."1" means you can use the cell and "0" means the cell is blocked. You can move in 4 directions left, right, top, bottom. Every...read more
Ans. 
• I gave recursion with backtracking solution to the interviewer, in which we explore every path and find the minimum cost.
Answered by CodingNinjas
View 4 more answers
Q2. Minimum Cost to Buy Oranges
You are given a bag of size 'W' kg and provided with the costs of packets with different weights of oranges as a list/array with the name 'cost'. Every i-th position in the cost ...read more
Ans. 
• This was the same as rod cutting dp problem, in place of maximum I have to minimize total cost. So I gave the interviewer first recursion approach, then he asked me to optimize it. After that, I gave dynamic programming solution.
Answered by CodingNinjas
View 5 more answers

Round duration - 60 minutes
Round difficulty - Easy

It was a subjective pen and paper coding round. Interviewer gave me one coding question that is: 

Q1. Snake and Ladder
Given a snake and ladder board, find the minimum number of dice throws required to reach the destination or last cell from source or 1st cell. Basically, the player has total control over t...read more
Ans. 
• I gave the interviewer Queue based approach. I basically considered the given board as a directed graph with number of vertices equal to the number of cells, and then our solution will be the shortest path from source to destination. The interviewer gave me test cases and asked me to dry run the code on that cases, in the first attempt there were some mistakes, which I corrected, and at last, the interviewer was satisf
Answered by CodingNinjas
View 2 more answers

Round duration - 90 Minutes
Round difficulty - Easy

The round was scheduled at 10 AM on 2nd August, 2019, But it started a little late due to some issues in Lab devices. The test started in a full screen mode and no one was allowed to exit full screen mode.

Q1. Remainder When Divided By 11
You are given a number N. You need to find the remainder when N is divided by 11.
Note :
Number N may be very large.
Input format :
The first line contains an integer '...read more
Ans. Using Modulo Property
1. Since the number is very large we can not simply calculate N % 11.
2. Now, any number say 256 % 11 can be calculated as (25*10 + 6)%11. Which in turn can be calculated as (( 25*10)%11+ 6)%11 or ( (25%11)*10 + 6)%11. Similarly 25%11 can be calculated as (2*10+5)%11. Therefore , 256 %11 can be finally calculated as ( ( (2*10 + 5)%11 )*10 + 6)%11.
3. So, the idea is to store the number N in string Str.
4. Take a ...read more
Answered by CodingNinjas
Add your answer
Q2. Missing Number
You are given an array/list ‘BINARYNUMS’ that consists of ‘N’ distinct strings which represent all integers from 0 to N in binary representation except one integer. This integer between 0 to...read more
Ans.  Convert to integers (Sorting)
In this approach, we will create an array of integers ‘nums’, by converting each string present in list ‘binaryNums’ in the integers they represent.
A binary string can be converted into a respective integer by simply traversing from rightmost character (least significant bit) to leftmost character (most significant bit) and for each position of set bit i.e (index where char is ‘1’) we add ...read more
Answered by CodingNinjas
View 3 more answers

Round duration - 60 Minutes
Round difficulty - Medium

It was a F2F interview. The interviewer was very friendly and was working as an SDE II in Consumers team. He started with quick intro of himself and then asked mine. Then jumped into coding question. He was monitoring my every single activity throughout the interview and told me ignore whenever I type something on my laptop.

Q1. Fish Eater
There is a river which flows in one direction. One day, the river has 'N' number of fishes. You are given an array 'FISHES' of integers representing the size of 'N' fishe...read more
Ans. Checking previous fishes
The first approach would be to simply check if a fish will be alive at the end or not. We can find this just by checking if a fish has any bigger fish behind it or not.
 
The steps are as follows:
 
• Traverse over each fish.
• For each fish check if it has any bigger fish behind it.
• If it does not have any bigger fish behind it just increase the count of remaining fishes.
• Return the count of re...read more
Answered by CodingNinjas
View 1 more answer
Q2. Fishmonger
A fishmonger wants to bring his goods from port to the market. On his route, he has to traverse an area with many states. He has to pay a toll at each border.
He is a good businessman. He want...read more
Ans. Brute Force
In this approach, we have to make a recursive function that returns the minimum toll needed to reach the N-1 node within the given time limit. We have to create a visited array of size N to maintain which vertices are already visited.
1. We will check If we reached the last node, then return the currToll. This will act as the base case of the recursive function.
2. We will call the recursive function on all the adja...read more
Answered by CodingNinjas
View 1 more answer

Round duration - 75 Minutes
Round difficulty - Medium

It was a F2F interview. The interviewer was very friendly and was working as an SDE III in Payments team. He started with quick intro of himself and then asked mine. He asked me about the project I mentioned in my resume and some questions regarding the project. Then jumped into coding question. He was monitoring my every single activity throughout the interview.

Q1. Battalions and tanks
Let there be ‘N’ battalions of soldiers and ‘M’ tanks. You are also given an array/list of length ‘N’ whose i-th index denotes the number of soldiers in the i-th battalion. You are sup...read more
Ans. Max-heap based approach.
Let us first assign 1 tank to each battalion because the number of tanks assigned to any battalion will definitely be greater than or equal to 1. Now, if any extra tank is left then assigning the tank to the battalion having the maximum ratio of soldiers to the number of tanks will be an optimal choice. Because the maximum ratio will definitely decrease if we assign the next tank to this battali...read more
Answered by CodingNinjas
View 1 more answer
Q2. Diagonal Traversal of a binary tree.
You have been given a binary tree of integers. You are supposed to find the diagonal traversal(refer to Example) of the given binary tree.
Example:
Consider lines at...read more
Ans. Map based approach
The idea is to use the Map to store all the nodes of a particular diagonal number. We will use preorder traversal to update the Map. The key of the Map will be the diagonal number and the value of the Map will be an array/list that will store all nodes belonging to that diagonal. 
 
The steps are as follows:
 
1. Assign the diagonal number of the root as 0.
2. Do a preorder traversal of the binary...read more
Answered by CodingNinjas
Add your answer

Round duration - 120 minutes
Round difficulty - Hard

Q1. Round Robin Scheduling
You have been given the ‘N’ process with process id’s from 1 to ‘N’. For each process, you are given the arrival time and burst time. You are also provided with the time quantum. Now...read more
Ans. Queue based approach.
The basic idea of this approach is to use a queue to solve the problem. We’ll keep the process in the queue which needs to be executed. And when a process is executed for the time quantum time, then we’ll push it to the end of the queue.

 
Consider the following steps:
1. Sort the processes in increasing order of arrival time.
2. Create an array/list “remTime” to store the remaining time for each proces...read more
Answered by CodingNinjas
Add your answer