Interview Questions and Answers for 'Amazon' | Search Interview Question

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Q281. What are the different layers of cloud computing ?

Infrastructure

Ans. Paas - Platform as a service
Iaas - Infrastructure as a service
Saas - Software as a service

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Q282. What is AWS or Amazon Web Services ?

Amazon Web Services (AWS)

Ans. These are the platforms or set of services provided by Amazon for cloud services , database storage , content delivery and other business applications and solutions.

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Q283. Given a string and index for the opening bracket, find the index of matching closing bracket.

Core Java

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Q284. Given a string with multiple opening and closing brackets, determine if the string is valid or not ( to see if the string has all closing brackets for each opening bracket ) ?

Core Java

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Q285. How to convert a bst to doubly linked list

Algorithm

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Q286. Write code to find the node where two linked lists intersect.

Algorithm

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Q287. Write a function that returns the depth of a tree.

Algorithm

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Q288. how to get most significant bit from a byte?

Core Java

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Q289. Write a program to reverse words of a sentence.

Core Java

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Q290. Write code to check if a Binary tree is symmetrical

Algorithm

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Q291. Explain bubble sort.

Algorithm

Ans. array is traversed from first element to last element. Here current element is compared with next element. If current element is greater than next element it is swapped.

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Q292. Given array of integers, find first two numbers that adds up to 10.

Core Java

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Q293. What is Amazon S3 ?

Amazon Web Services (AWS)

Ans. Amazon Simple Storage Service or S3 is object storage with a simple web service interface to store and retrieve any amount of data from anywhere on the web.

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Q294. Write a program to print the index of the first non repeated character in a java string

Core Java

Ans. public class BuggyBread1{
public static void main (String args[]) {
   String str = "hheello world";
   char[] charArray = str.toCharArray();
   char selectedChar = 'a';
   for(char char1: charArray){
      if(!str.contains(Character.toString(char1).concat(Character.toString(char1)))){
         selectedChar = char1;
         break;
      }
   }
   System.out.println(str.indexOf(Character.toString(selectedChar)));
}
}

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Frequently asked in high end product companies.

Q295. Write code for LRU Cache

Core Java

Ans. https://www.geeksforgeeks.org/lru-cache-implementation/

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Q296. Write a Program to check if 2 strings are Anagrams ?

Core Java

Ans. public void checkIfAnagram(String str1,String str2){
boolean anagram = true;
for(char c:str1.toCharArray()){
if(!str2.contains(String.valueOf(c))){
System.out.println("Strings are Anagrams");
anagram = false;
}

if(anagram == true){
System.out.println("Strings are not Anagrams");
}
}
}

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Q297. How would you count the number of words in a string consisting of uneven number of spaces between words( not dictionary words)? With and without library functions.

Core Java

Ans. package com.string;

import java.util.Scanner;

public class String13 {
public static void main(String[] args) {
System.out.println("Enter Sentence");
Scanner sc=new Scanner(System.in);
String sentence=sc.nextLine();
String[] words=sentence.split(" ");
int count=0;
for (String string : words) {
string.trim();
if(!string.equals("")){
count++;
System.out.println(string " " count);
}
}
}
}

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Advanced level question usually asked in High end product companies. Have been asked in Google and Amazon (Based on 1 Feedback)

Q298. Describe, in general, how java's garbage collector works ?

Core Java

Ans. The Java runtime environment deletes objects when it determines that they are no longer being used. This process is known as garbage collection. The Java runtime environment supports a garbage collector that periodically frees the memory used by objects that are no longer needed. The Java garbage collector is a mark-sweep garbage collector that scans Java dynamic memory areas for objects, marking those that are referenced. After all possible paths to objects are investigated, those objects that are not marked (i.e. are not referenced) are known to be garbage and are collected.

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Very frequently asked to Fresh graduates.

Q299. What is the difference between Encapsulation and Abstraction?

Core Java

Ans. 1.Abstraction solves the problem at design level while encapsulation solves the problem at implementation level

2.Abstraction is used for hiding the unwanted data and giving relevant data. while Encapsulation means hiding the code and data into a single unit to protect the data from outside world.

3. Abstraction lets you focus on what the object does instead of how it does it while Encapsulation means hiding the internal details or mechanics of how an object does something.

4.For example: Outer Look of a Television, like it has a display screen and channel buttons to change channel it explains Abstraction but Inner Implementation detail of a Television how CRT and Display Screen are connect with each other using different circuits , it explains Encapsulation.

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Frequently asked to fresh graduates.

Q300. Difference between Process and Thread ?

Operating System

Ans. Process is a program in execution whereas thread is a separate path of execution in a program.

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.

Q301. What is the difference between ArrayList and LinkedList ?

Core Java

Ans. Underlying data structure for ArrayList is Array whereas LinkedList is the linked list and hence have following differences -

1. ArrayList needs continuous memory locations and hence need to be moved to a bigger space if new elements are to be added to a filled array which is not required for LinkedList.

2. Removal and Insertion at specific place in ArrayList requires moving all elements and hence leads to O(n) insertions and removal whereas its constant O(1) for LinkedList.

3. Random access using index in ArrayList is faster than LinkedList which requires traversing the complete list through references.

4. Though Linear Search takes Similar Time for both, Binary Search using LinkedList requires creating new Model called Binary Search Tree which is slower but offers constant time insertion and deletion.

5. For a set of integers you want to sort using quicksort, it's probably faster to use an array; for a set of large structures you want to sort using selection sort, a linked list will be faster.

Sample Code for ArrayList

Sample Code for LinkedList

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Q302. Difference between TCP and UDP ?

Networking

Ans. http://www.cyberciti.biz/faq/key-differences-between-tcp-and-udp-protocols/

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Frequently asked to fresh graduates and less experienced developers. Among the first few questions in many interviews.

Q303. What are the difference between composition and inheritance in Java?

Core Java

Ans. Composition - has-a relationship between objects.
Inheritance - is-a relationship between classes.

Composition - Composing object holds a reference to composed objects and hence relationship is loosely bound.
Inheritance - Derived object carries the base class definition in itself and hence its tightly bound.

Composition - Used in Dependency Injection
Inheritance - Used in Runtime Polymorphism

Composition - Single class objects can be composed within multiple classes.
Inheritance - Single class can only inherit 1 Class.

Composition - Its the relationship between objects.
Inheritance - Its the relationship between classes.

Sample Code for inheritance

Sample Code for composition

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Very Frequently asked. Have been asked in HCL Technologies very frequently ( based on 3 feedback ). Among first few questions in many interviews.

Q304. Differences between abstract class and interface ?

Core Java

Ans. Abstract classes can have both abstract methods ( method declarations ) as well as concrete methods ( inherited to the derived classes ) whereas Interfaces can only have abstract methods ( method declarations ).

A class can extend single abstract class whereas it can implement multiple interfaces.

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