Amazon Software Developer Intern Interview Questions, Process, and Tips

Round duration - 60 minutes
Round difficulty - Medium

The interviewer was very friendly and introduced herself. She told me that she had two coding problems for this round.

Q1. 
Spiral Order Traversal of a Binary Tree
Given a binary tree with N nodes, your task is to output the Spiral Order traversal of the binary tree.
Input:
The input consists of a single line containing elem...read more
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Q2. 
Find Row With Maximum 1's in a Sorted 2D Matrix
You are provided with a 2D matrix containing only the integers 0 or 1. The matrix has dimensions N x M, and each row is sorted in non-decreasing order. Your...read more
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Round duration - 70 minutes
Round difficulty - Medium

This round was held 30 minutes after the 2nd round. There were two interviewers and both introduced themselves. Both of them were friendly and made me comfortable for the round.

Q1. 
Sort Array by Set Bit Count
You have an array of N positive integers. Your goal is to sort this array in descending order based on the number of set bits in the binary representation of each integer.
In ...read more
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Q2. 
Rotting Oranges Problem Statement
You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:
• 0 - representing an empty cell
• 1 - representing a fre...read more
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Round duration - 80 minutes
Round difficulty - Medium

This round was scheduled in the evening hours and all the participants were required to fill a form which was shared 2 days prior to the test date. This form was filled out probably for the security reasons and to ensure that no one disinterested participant gives the test.

Q1. 
First Negative Integer in Every Window of Size K
Given an array of integers 'ARR' and an integer 'K', determine the first negative integer in every contiguous subarray (or window) of size 'K'. If a window...read more
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Q2. 
Maximum Sum of Non-Adjacent Nodes in a Binary Tree
Given a binary tree with integer values assigned to each node, select nodes such that their sum is maximum, ensuring no two adjacent nodes are picked.
I...read more
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Round duration - 60 minutes
Round difficulty - Medium

Interview stared at 11:00 am and went for 90 min.
Interview was held in zoom
Environment was very much user friendly

Q1. 
Validate Binary Search Tree (BST)
You are given a binary tree with 'N' integer nodes. Your task is to determine whether this binary tree is a Binary Search Tree (BST).
BST Definition:
A Binary Search 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
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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
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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
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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
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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
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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
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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 - 75 Minutes
Round difficulty - Medium

Q1. 
Number of Islands Problem Statement
You are provided with a 2-dimensional matrix having N rows and M columns, containing only 1s (land) and 0s (water). Your goal is to determine the number of islands in t...read more
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Q2. 
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
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Round duration - 60 Minutes
Round difficulty - Medium

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
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Q2. 
Pair Sum Problem Statement
You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to find and return a list of all pairs of elements where each sum of a pair equals 'S'.
Note:
...read more
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Round duration - 60 Minutes
Round difficulty - Medium

it was pure DSA round, no HR round was there after this

Q1. 
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
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Round duration - 120 Minutes
Round difficulty - Medium

Around 4-5 pm
2 coding questions
7 debugging and output questions
20-30 aptitude questions
A section to test psychology based on various questions and situations.

Q1. 
Clone Linked List with Random Pointer Problem Statement
Given a linked list where each node has two pointers: one pointing to the next node and another which can point randomly to any node in the list or ...read more
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Q2. 
Next Smaller Element Problem Statement
You are provided with an array of integers ARR of length N. Your task is to determine the next smaller element for each array element.
Explanation:
The Next Smalle...read more
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Round duration - 50 Minutes
Round difficulty - Medium

Timing - 4pm
Just asked one question based on DSA and asked to make the code modular and well indented.
Didn’t even ask for introduction.

Q1. 
Rotting Oranges Problem Statement
You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:
• 0 - representing an empty cell
• 1 - representing a fre...read more
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Round duration - 60 Minutes
Round difficulty - Medium

Started at 4pm
Interviewer introduced himself and then asked me for a brief introduction.
Went ahead to ask 2 DSA based questions.

Q1. 
Merge k Sorted Linked Lists
You are provided with 'K' sorted linked lists, each sorted in increasing order. Your task is to merge all these lists into one single sorted linked list and return the head of ...read more
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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
Add your answer

Round duration - 150 Minutes
Round difficulty - Medium

The test was on AMCAT platform.
The test was of 2.5 hours , web-proctored and switching between tabs was not allowed.

Test consist of 4 sections:

1 Debug section which had 7 questions to correct/write the code. (20min)
2 Coding section having 2 questions. (70 min)
3 Logical Reasoning section. (35 min)
4 Workstyle assessment. (20 min)

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
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Q2. 
Subtree of Another Tree Problem Statement
Given two binary trees, T and S, determine whether S is a subtree of T. The tree S should have the same structure and node values as a subtree of T.
Explanation:
...read more
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Round duration - 60 Minutes
Round difficulty - Hard

Interview was conducted on Amazon Chime platform and for coding, link was shared on which I had to code.
Two questions were given to me and requested to solve in the desired time. 
Interviewer was friendly and supportive.

Q1. 
Reachable Nodes Problem Statement
You are provided with a graph containing 'N' nodes and 'M' unidirectional edges. Your task is to determine the number of nodes that can be reached from each node 'i', whe...read more
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Q2. 
Squares of a Sorted Array Problem Statement
You are given an array/list ARR consisting of N integers. Your task is to generate a new array/list containing the squares of each element in ARR, with the resu...read more
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Round duration - 45 Minutes
Round difficulty - Medium

Interview was conducted on Amazon Chime platform and for coding, link was shared on which I had to code.
Three questions were given to me and requested to solve in the desired time. 
Interviewer was friendly and supportive.

Q1. 
Valid String Problem Statement
Given a string S consisting solely of the characters '(', ')', and '*', determine if it is a valid string.
Definition of Valid String:
1. Every left parenthesis '(' must h...read more
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Q2. 
Convert a Binary Tree to its Sum Tree
Given a binary tree of integers, convert it to a sum tree where each node is replaced by the sum of the values of its left and right subtrees. Set leaf nodes to zero.
...read more
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Round duration - 90 minutes
Round difficulty - Medium

There were 30 MCQ and 7 Debugging question and two coding question
Then technical interview 1
Then last technical plus hr Interview

Q1. 
Flatten BST to a Sorted List
The objective is to transform a given Binary Search Tree (BST) into a right-skewed BST, effectively flattening it into a sorted list. In the resulting structure, every node's ...read more
Ans. 
Transform a Binary Search Tree into a right-skewed BST, flattening it into a sorted list.
• Implement a function to flatten the BST into a sorted list by linking nodes through right children.

• Traverse the BST in-order and adjust the pointers to create the right-skewed structure.

• Ensure that every node's left child is NULL in the resulting flattened BST.

• Output the values of nodes in the skewed BST in level order for each tes...read more
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Q2. 
Prerequisite Task Completion Verification
Given a positive integer 'N', representing the number of tasks, and a list of dependency pairs, determine if it is possible to complete all tasks considering thes...read more
Ans. 
Given tasks and dependencies, determine if all tasks can be completed based on prerequisites.
• Create a graph representation of tasks and dependencies.

• Use topological sorting to check if there is a cycle in the graph.

• Return 'Yes' if no cycle is found, 'No' otherwise.
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Round duration - 60 minutes
Round difficulty - Medium

Two questions were given to me and requested to solve in the desired time.

Q1. 
Sort Linked List Based on Actual Values
Given a Singly Linked List of integers that are sorted based on their absolute values, the task is to sort the linked list based on the actual values.
The absolute...read more
Ans. 
Sort a Singly Linked List based on actual values instead of absolute values.
• Traverse the linked list and store the nodes in an array.

• Sort the array based on the actual values of the nodes.

• Reconstruct the linked list using the sorted array.
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Q2. 
Convert a Binary Search Tree (BST) to a Greater Sum Tree
Given a Binary Search Tree of integers, transform it into a Greater Sum Tree where each node's value is replaced with the sum of all node values gr...read more
Ans. 
Convert a Binary Search Tree to a Greater Sum Tree by replacing each node's value with the sum of all node values greater than the current node's value.
• Traverse the BST in reverse inorder (right-root-left) to visit nodes in descending order.

• Keep track of the running sum of visited nodes and update each node's value with this sum.

• Modify the BST in place without creating a new tree.

• Example: For input 11 2 29 1 7 15 40 -1...read more
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Round duration - 60 minutes
Round difficulty - Medium

Two questions were asked but I don't remember the second one.

Q1. 
Split Array into K Subarrays
You are given an array ARR of size N and an integer K. Your task is to split ARR into K sub-arrays such that the maximum sum obtained from these K subarrays is minimized.
Inp...read more
Ans. 
Split an array into K subarrays to minimize the maximum sum obtained from the subarrays.
• Sort the array in descending order to get the maximum sum possible.

• Use binary search to find the minimum possible value of the maximum sum.

• Consider the constraints to optimize the solution.

• Example: For N=4, K=3, ARR=[1, 2, 3, 4], the minimum possible value of the maximum sum is 4.
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