Amazon Software Developer Intern Interview Questions, Process, and Tips

2 OA questions the difficulty like LC medium hard

Q1. 2 data structures and algorithms questions
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Q2. Longest substring without repeating characters
Ans. 
Find the longest substring without repeating characters in a given string.
• Use a sliding window approach to keep track of the current substring without repeating characters.

• Use a hash set to store the characters in the current substring and check for duplicates.

• Update the start index of the window when a duplicate character is found to maintain the longest substring without repeating characters.
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Round duration - 90 Minutes
Round difficulty - Medium

Part 1. 7 Bug fixes 
Part 2. 2 DSA Medium Hard Questions
Part 3: Behavioral Questions MCQ

Q1. 
Container with Most Water Problem Statement
Given a sequence of 'N' space-separated non-negative integers A[1], A[2], ..., A[i], ..., A[n], where each number in the sequence represents the height of a lin...read more
Ans. 
Given a sequence of non-negative integers representing the height of lines on a cartesian plane, find two lines that form a container with the maximum area of water.
• Use two pointers approach to find the maximum area

• Start with the widest container and gradually move the pointers towards each other

• Calculate the area at each step and update the maximum area

• The area is calculated as the minimum height of the two lines mult
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Q2. 
Minimum Travel Cost Problem
You are given a country called 'Ninjaland' with 'N' states, numbered from 1 to 'N'. These states are connected by 'M' bidirectional roads, each with a specified travel cost. Th...read more
Ans. 
The task is to select 'N' - 1 roads in a country with 'N' states, such that the tourist bus can travel to every state at least once at minimum cost.
• The problem can be solved using a minimum spanning tree algorithm, such as Kruskal's algorithm or Prim's algorithm.

• Create a graph representation of the country using the given roads and their costs.

• Apply the minimum spanning tree algorithm to find the minimum cost roads tha...read more
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Round duration - 80 minutes
Round difficulty - Medium

Face to Face DSA online round conducted on Amazon Chime platform.

Q1. 
First Missing Positive Problem Statement
You are provided with an integer array ARR of length 'N'. Your objective is to determine the first missing positive integer using linear time and constant space. T...read more
Ans. 
The task is to find the lowest positive integer that does not exist in the given array of integers.
• Iterate through the array and mark the positive integers as visited using the array indices.

• Iterate through the marked array and return the index of the first unmarked element.

• If all positive integers are marked, return the length of the array + 1 as the missing positive integer.
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Q2. 
Simplify Directory Path Problem Statement
You are provided with a directory path in Unix-style notation, and your task is to simplify it according to given rules.
In a Unix-style file system:
• A dot (...read more
Ans. 
The task is to simplify a given Unix-style directory path and determine the final destination.
• Replace multiple slashes with a single slash

• Handle dot (.) by ignoring it

• Handle double dot (..) by removing the previous directory from the path

• Ensure the simplified path starts with a slash and does not have a trailing slash
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Round duration - 60 minutes
Round difficulty - Easy

Face to Face DSA Round where I was asked 2 coding questions

Q1. 
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
Ans. 
Given an array and a target sum, find all pairs of elements in the array that add up to the target sum.
• Create an empty list to store the pairs

• Iterate through the array and for each element, check if there is a complement (target sum minus the current element) in the array

• If a complement is found, add the pair (current element, complement) to the list

• Sort the list of pairs in non-decreasing order of their first value

• If ...read more
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Q2. 
Frequency in a Sorted Array Problem Statement
Given a sorted array ARR and a number X, your task is to determine the count of occurrences of X within ARR.
Note:
• If X is not found in the array, return...read more
Ans. 
The task is to count the number of occurrences of a given number in a sorted array.
• Use binary search to find the first and last occurrence of the given number in the array.

• Subtract the indices of the first and last occurrence to get the count.

• Handle the case when the number is not found in the array.
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Round duration - 50 Minutes
Round difficulty - Easy

Rounds are technically based on DSA and the projects that I mentioned, and it will be last at least 50 minutes.

Q1. 
Valid Sudoku Problem Statement
You are given a 9 X 9 2D matrix named MATRIX which contains some cells filled with digits (1 to 9) and some cells left empty (denoted by 0).
Your task is to determine if th...read more
Ans. 
The task is to determine if a given 9x9 matrix can be filled with digits 1-9 to form a valid Sudoku solution.
• Iterate through each cell in the matrix.

• For each empty cell, try filling it with a digit from 1-9 and check if it satisfies the Sudoku conditions.

• Use helper functions to check if the digit is valid in the current row, column, and sub-matrix.

• If a valid digit is found, recursively fill the next empty cell.

• If all c...read more
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Very simple implementation questions

Q1. Number of connected components in a grid
Ans. 
Count the number of connected components in a grid
• Use Depth First Search (DFS) or Breadth First Search (BFS) to traverse the grid

• Keep track of visited nodes to avoid revisiting them

• Each connected component will have its own set of connected nodes
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Good knowledge of DSA is the key to solving the 2 questions

2 questions on hackerrank easy problems

Q1. Easy standard problem on array
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Q2. Medium standard problem on matrix
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