# Amazon Interview Experience | Set 375 (On Campus for Internship)

Recently, Amazon visited our campus to recruit interns and FTEs. There were 3 rounds in all – 1 Online Round followed by 2 F2F Interviews

Round 1: Online Round (90 minutes)
There were 2 coding questions and 20 MCQs mostly on Time Complexities (Master Theorem), Logical Reasoning, Data Structures and Algorithms, around 2 from OS, DBMS and Networking each.

The 2 coding questions were:

1. Find the sum of lengths of non-overlapping contiguous subarrays with k as the maximum element.
```   Ex: Array: {2,1,4,9,2,3,8,3,4} and k = 4
Ans: 5
{2,1,4} => Length = 3
{3,4}   => Length = 2
So, 3 + 2 = 5 is the answer
```

2. You are given an array A where A[i] (1-based indexing) denotes the number of chocolates corresponding to each station. When we move from station i to station i+1 we get A[i] – A[i+1] chocolates for free. Note that if this number is negative, we lose that many chocolates. We can only move from station i to station i+1 and that too if and only if we have non-negative number of chocolates with us. Given that cost of one chocolate is Rs. P , our task is to find the minimum cost incurred in reaching station n from the first station (station 1).

```Ex: A: {1,2,3} and P = 10
Ans: 30
To reach station 1 from the starting station, we need to buy 1 chocolate
To reach station 2 form station 1, we get A[1] - A[2] = -1 chocolates i.e. we lose 1 chocolate. Hence, we need to buy 1 chocolate.
Similarly, we need to buy 1 chocolate to reach station 3 from station 2.
Hence, total cost incurred = (1+1+1)*10 = 30
```
3. Out of around 150 students, 26 were shortlisted for Round 2.

Round 2: FTF Interview (Around 30-40 minutes)
First, the interviewer told me to introduce myself and then asked 3 coding questions:

1. Search for an element in a row-wise and column-wise sorted 2D Matrix
I started with a O(R*C) solution, followed it up with an O(RlogC) solution and finally gave the O(R+C) solution.
2. Given an array of n elements and a number, find a pair in the array with sum equal to that number.
This question was followed up with finding a triplet with sum equal to Zero.
3. I was provided with a function int getval(int x) which basically takes the value of x and returns f(x). Given that f(x) is a monotonically increasing function, my task was to find the smallest value of x such that f(x) > 0.

Round 3: FTF Interview (Around 30 minutes)
The interviewer once again asked me to introduce myself and asked 3 questions:

1. What is Data Abstraction. Explain it with a real-life example.
2. What are infix and postfix expressions. He then asked me to write a pseudo-code for converting infix expression to postfix expression.
3. Multiply 2 numbers without using Multiplication or Division operator, Bitwise operators or any loop.
4. I gave him a recursive approach and he was pretty happy with it

Out of the 26 selected for the interviews, 13 were finally selected for internship.

During my preparation GEEKSFORGEEKS, indeed, was a great help. Preparing from articles under DS and Algo section would give anybody a definite chance to clear all rounds. A big thank you to other geeks as well for sharing their interview experiences as going through past experiences was the perfect way to end my preparations.

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