Uber Interview Questions, Process, and Tips

Round duration - 120 minutes
Round difficulty - Easy

It was a mix of mathematical aptitude, logical ability, and puzzles along with 2 programming questions of easy and medium levels. Time was enough and no sectional time was present. 1-2 MCQs on SQL was also present.

Q1. Boolean Matrix
Given a 2-dimensional boolean matrix mat of size N x M, modify the matrix such that if an element is 1, set its entire row and column to 1 i.e. if mat[i][j] = 1, then make all the elements o...read more
Ans. 
You need to make the modifications in the input matrix.
You do not need to print anything, it has already been taken care of.
Answered by CodingNinjas
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Round duration - 60 minutes
Round difficulty - Easy

It was an online video interview round on HackerEarth with a simultaneous code option. It was mostly justifying your resume in the first 15 minutes. After that OOPS was majorly asked. Basics of programming including questions on STL were asked. A class that required inheritance was asked by the interviewer to write. I was helped by the interviewer if I got stuck somewhere, Some questions on the implementation of hashmaps and priority queues were also asked. A puzzle was asked which luckily struct to me at that moment.

Q1. Connect n ropes with minimum cost
You have been given 'N' ropes of different lengths, we need to connect these ropes into one rope. The cost to connect two ropes is equal to sum of their lengths. We need to...read more
Ans. 
Input format :
The first line of input contains an integer value 'N'. It denotes the total number of ropes.

The second line of input contains 'N' single space-separated integers representing the length of each rope i.e. a1, a2, a3, ... an.
Output Format :
The only line of output will contain an integer, the minimum cost for connecting all the ropes.
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Round duration - 60 minutes
Round difficulty - Easy

Timing: evening
Environment: Online round took at home

Q1.  Smallest Subarray with K Distinct Elements
Given an array 'A' consisting of 'N' integers, find the smallest subarray of 'A' containing exactly 'K' distinct integers.
Note ...read more
Ans. 
At first sight this can be solved easily by using two loops to iterate over contiguous subarrays in O(n^2) and counting number of arrays and breaking the outer loop if number of odds exceed 'k'.

Optimised solution is to take two pointer approach where right pointer is incremented till num of odds not exceed 'k'. If limit is reached, increment left pointer and add number of arrays (right - left+1)*(right-left)/2 to the r
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Round duration - 90 minutes
Round difficulty - Medium

Machine coding round

Q1. Design and code publisher subscriber based messaging queue supporting following features:
Design and code publisher subscriber based messaging queue supporting following features:
1. New topic creation
2. Mul...read more
Ans. 
1. I drafted LLD by defining classes - methods and members.
2. I discussed the approach and working of LLD to fit the given features
3. I live coded the classes and logic using core Java on my machine.
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Round duration - 60 minutes
Round difficulty - Medium

Q1. Rat In a Maze All Paths
You are given a 'N' * 'N' maze with a rat placed at 'MAZE[0][0]'. Find and print all paths that rat can follow to reach its destination i.e. 'MAZE['N...read more
Ans. Backtracking Approach
Initialize, all the cells of the solution matrix used to print the path matrix to 0. First, you cannot make use of the existing maze to print the solution maze as you have to distinguish b/w 1 of maze or 1 of ‘SOLUTION matrix.
 
Form a recursive function, which will follow a path and check if the path reaches the destination or not. If the path does not reach the destination then backtrack and t...read more
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Round duration - 60-90 minutes
Round difficulty - Medium

Q1. Design stock exchange system
I was required to describe a typical stock exchange system design.
He asked me to begin with defining API contracts. Problem was open ended. Started with clarifying the scope and...read more
Ans. 
Tip 1 : Revise general distributed system concepts thoroughly.
Tip 2 : Practice as many design problems as possible with time constraints. Try to discuss approaches with friends.
Tip 3 : Clarify as many doubts and assumptions as possible wit h the interviewer before jumping to the solution.
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Round duration - 60 minutes
Round difficulty - Medium

Hiring Manager round

Q1. General Questions
1. Brief description of past work.
2. Recent challenging bug/issue solved.
3. Design description of one of the projects.
4. SDLC, tooling, agile related discussions.
Ans. 
Tip 1 : Revisit and recollect your past experiences in detail with a focus on learnings, challenges, conflicts etc.
Tip 2 : Prepare general behavioural and situational questions for the role.
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Round duration - 60 minutes
Round difficulty - Medium

It started with an informal talk after he gave his introduction. We talked about the cyclone that was going to be there and what I did in my internship and my previous projects. Then we moved to questions. After solving both questions he asked if I had questions.

Q1. Kth Largest Element in an Array
You are given an array consisting of 'N' distinct positive integers and a number 'K'. Your task is to find the kth largest element in the array.
Example:
C...read more
Ans. 
To solve the question using a max heap, make a max heap of all the elements of the list. Run a loop for k-1 times and remove the top element of the heap. After running the loop, the element at top will be the kth largest element, return that. Time Complexity : O(n + klogn)

The question can also be solved using a min heap. 
 
Approach :
 
1. Create a min heap class with a capacity of k
 
2. When the heap re...read more
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Q2. Minimum time required to rot all oranges
You have been given a grid containing some oranges. Each cell of this grid has one of the three integers values:
Value 0 - representing an empty cell.
Value...read more
Ans. 
BFS can be used here. 
Algorithm : 

1. Create an empty queue Q. 
 
2. Find all rotten oranges and enqueue them to Q. Also, enqueue a delimiter to indicate the beginning of the next time frame.
 
3. Run a loop While Q is not empty
 
4. Do following while delimiter in Q is not reached
4.1. Dequeue an orange from the queue, rot all adjacent oranges. While rotting the adjacent, make sure that the time ...read more
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Round duration - 45 minutes
Round difficulty - Easy

This was a design round.

Q1. System Design Question
How to stream an image such that all clients see the same image at the same time? You need to take care of delays, network problems. He kept on adding new elements like compression, s...read more
Ans. 
Tip 1 : Firstly, remember that the system design round is extremely open-ended and there’s no such thing as a standard answer. Even for the same question, you’ll have a totally different discussion with different interviewers.

Tip 2 : Before you jump into the solution always clarify all the assumptions you’re making at the beginning of the interview. Ask questions to identify the scope of the system. This will clear the...read more
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