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Amazon Interview | Set 108 (On-Campus)

  • Difficulty Level : Hard
  • Last Updated : 20 Jun, 2019

Dear, I just got hired by Amazon in my campus placement drive. Below are the details of my selection process with amazon.

Fist Round(Online):
20 MCQ questions and 2 Coding Questions .
Coding Questions :
1. Merge overlapping intervals(Very well known repeating problem).
2. Given a singly linked list you have to subtract the value of first node from the last node and so on until you reach the middle node.
Eg: Input: 5 -> 4 -> 3 -> 2 -> 1
Output: 4 -> 2 -> 3 -> 2 -> 1

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1) Given a sorted circular link list and a pointer to random node, now insert a new node. I did it , but i used if and else for some special cases in my code so he asked me to do it without if else for special cases (generic & simple code ).

2) Given a pointer to node in tree and a root pointer. Print all the nodes which are at a distance k from the given node.
1) He gave me task scheduling problem:
Given a set of modules, some modules depend on previous modules and can only be executed, if the requirements of that module is complete.

Eg: module A depends on module B,C 
   module B depends on module C and D
   module C depends on E
   module E depends on D
   module D doesn't depend on any other module 

so he asked me to give a schedule for above modules such that when a module is executed then all requirements of that module are complete.
so answer would be D E C B A

2) Given a string of letters from alphabet. Remove all pairs(2 consecutive same character) of characters which occur consecutively.And do it recursively on remaining string.

Eg given string abcdaadhhhhhzppzl
  then output string should be : abchl 

Hint: He asked me to use some data structure for it .

3) Given a binary tree set the sibling pointers . I told him that i already know the question so he said code it .

4) He asked me about hashing .
4.1 He asked me about complexity . I told him about O(logn) and O(1) .
4.2 Then he asked me about how do you get O(1). I told him my approach . He said how will you rehash it when required . I told him that i will use extra memory and copy the hash map . Then i Optimized and did it in-place using a Boolean field.
4.3 Then he took this question to OS and asked me to do it using threads .
4.4 Asked me what all problems you will need to take care about this problem while using threads and give solution to it.

5) Discussion on my projects

He gave me 3 coding questions :
1) Given a number n find the number of valid permutations of a string formed using characters ‘(‘ and ‘)’ . A string is valid if it has matching opening and closing parenthesis .
Eg: given n=2 so you can have 2 possible permutations which are valid (()) and ()() .

2) Given a singly link list reverse every 3 nodes and if nodes are less than 3 then reverse them also.

Eg: Input:  1->2->3->4->5->6->7->8
    Output: 3->2->1->6->5->4->8->7 

3) Given a string of letters from alphabet insert frequency of each character in the string.

Eg: Input:  aaabbbccdefgggaaa
    Output: a3b3c2d1e1f1g3a3 

Time Complexity Required O(n) Space Complexity Required O(1)

Fourth Round (Bar Raiser):
It was a telephonic round with a collabedit screen shared on our laptops.

1) Tell me something about yourself .

2) He saw that i had given a seminar on cloud computing and sky computing so he started with cloud computing .Then he asked me why didn’t cloud computing exist 15 years ago .

3) What do you understand by 32 bit and 64 bit OS ? . He asked for explanations in terms of hardware and software . Then he asked me that will a 16 bit program run on 64 bit OS without any problem . He asked me what can be the reason for problem faced .

4) What happens when you type in your browser ? . He asked me for the set of activities that take place during this time . Then he went into asking how do you get to know the IP address of your ISP . Then after a lot of discussion he was satisfied .

5) Some questions about Complexity of a algorithm . Asked me to prove complexity of few sample codes .

6) Some questions about storage space of a variable( data segment , stack , heap , BSS ). Some questions about Macro preprocessors and there problems & solutions .

7) Some questions about error in sample code given (like returning non compatible pointer type or returning address of a local variable etc )

8) In DOS and Linux shell when we press the up arrow we get the recently used commands . He asked me to implement this facility. Then he asked me to do it if memory bound was very tight .

9) This was a question to check my analytic skills . We have customers using for buying phones. Let say we have a user who visits for buying mobile phone . He selects a mobile then fills his address details and then when he finally goes for payment then he gets to know that this phone is not available . So how can you improve the over all user experience . Then he asked me that will you suggest redirecting the user to some other site if the product is out of stock .

10) Some HR Questions like What are your areas of your Weaknesses ? What are you doing to improve on them ?

It was an amazing experience. Thanks a lot to GeeksforGeeks for helping me get my dream job 🙂

Suggestions/Tips :
1) Discuss your approach as many times as possible.
2) Don’t start Coding the problem until the interviewer asks you to do it.
3) Tell everything that you are thinking about the problem. They are more interested in knowing how you are approaching the problem.
4) Asks for hints if you are stuck up. They will help you.
5) If you don’t know answer to a question then please say it directly. It will save time for other questions.
6) First be confident about your approach then only code it.

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