Uber Software Developer Intern Interview Questions, Process, and Tips

Graphs ,arrays , Hashmaps and Heaps

Q1. Graphs related dfs
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Q2. Changes on graph structure
Ans. 
Changes on graph structure involve adding, removing, or modifying nodes and edges.
• Adding a new node to the graph

• Removing an existing node from the graph

• Modifying the weight of an edge in the graph
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Round duration - 90 minutes
Round difficulty - Easy

This round had 2 coding problems and we had to code it on hackerearth only.
The use of Outside IDE was forbidden.
The timing of test was 12:00 PM to 1:30 PM.

Q1. 
Meeting Rescheduling Challenge
Ninja is tasked with organizing a meeting in an office that starts at time ‘0’ and ends at time ‘LAST’. There are ‘N’ presentations scheduled with given start and end times....read more
Ans. Brute Force Approach
Algorithm:
 
• The idea here is to find the maximum sum subarray of size ‘K+1’, where the array will contain empty slots.
• First, we create an array named emptySlots[], to store the time duration in which there is no presentation.
• Run a loop to traverse all presentations, and in each iteration, add START[i] - END[i-1] (which gives a free slot between the ith presentation) into the array emptySlots[].
• N...read more
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Q2. 
Total Unique Paths Problem Statement
You are located at point ‘A’, the top-left corner of an M x N matrix, and your target is point ‘B’, the bottom-right corner of the same matrix. Your task is to calcula...read more
Ans. Recursive Approach
We can easily count the total number of paths by making a recursive algorithm.
 
The steps are as follows:
 
1. We are given a function UNIQUEPATHS(), which takes two integers ‘M’ and ‘N’ as parameters and returns a single integer. This will be the definition of our recursive function too.
2. As our base condition, we will check if our number of rows (‘M’) or a number of columns (‘N’) is equal to 1. If...read more
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Round duration - 90 minutes
Round difficulty - Medium

This round was coding round with discussion .
The interviewer tried to trick the questions and wanted to test how we respond if something is asked out of preparation.
The code we ran on Google Docs was checked on Online IDE if it ran for sample inputs.
Timing : 12:00 PM to 1:30 PM

Q1. 
Minimum Operations to Connect a Graph
You are given a graph with 'N' vertices labeled from 1 to 'N' and 'M' edges. In one operation, you can shift an edge from being between two directly connected vertice...read more
Ans. Breadth First Search.
For a graph with ‘N’ vertices to be connected, there must be at least ‘N’ - 1 edges in the graph. If a graph has less than ‘N' - 1 edges it is impossible to make the graph connected. Otherwise, it is always possible to make graph connected. As we need to find the minimum number of operations to make the graph connected we will think greedily. We will find the total number of connected components in...read more
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Q2. 
Snake and Ladder Problem Statement
Given a 'Snake and Ladder' board with N rows and N columns, where positions are numbered from 1 to (N*N) starting from the bottom left, alternating direction each row, f...read more
Ans. BFS
We will use Breadth-First Search to find the shortest path from cellNumber 1 to cellNumber N*N.
1. We will maintain a queue of cellNumber where the front of the queue will always contain a cell which can be reached by minimum dice throw from starting cell (cellNumber = 1).
2. Create a minDiceThrow array of size N*N initialise it with the maximum value (INT_MAX)
3. Start with pushing cellNumber 1 and updating minDiceThrow[1] = 0...read more
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Round duration - 75 minutes
Round difficulty - Hard

This was a problem solving round and lasted for 75 minutes. The interviewer gave me a very complicated question.
The round was held on Google Meet and I was supposed to tell him the approach and write code on shared Google Docs.

Q1. 
XOR Query Problem Statement
Assume you initially have an empty array called ARR. You are required to return the updated array after executing Q number of queries on this array.
There are two types of que...read more
Ans. Brute Force
Approach:
• It is a brute force approach where we will create an empty array initially of size 10^5 + 1.
• Now, whenever we have a query of type 1 we will insert the value of VAL in the array. And when the query of type 2 comes then we will iterate through our array and perform an XOR operation with VAL to every value present in our array.
• Finally, we will return our array.
 
Algorithm:
• Create an array ans.
• Now it...read more
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Round duration - 90 minutes
Round difficulty - Medium

There were a total of three questions of 100, 200, and 300 points respectively. Partial points were given if partial tests got passed for any problem. The Codesignal environment was similar to Hackerrank, so not much different. I think the test was held in the afternoon time.

Q1. 
Game of Stones Problem Statement
Two players, 'Ale' and 'Bob', are playing a game with a pile of stones. Your task is to determine the winner if both play optimally.
Rules of the Game:
1. On each turn, ...read more
Ans. Game Theory
• It is clear that if the number of stones is ‘1’ then ‘Ale’ wins the game. If ‘2’ then also ‘Ale’ wins the match, and if ‘3’ then ‘Bob’ wins the game.
• So we can observe that, if anyone has a chance to choose a stone from ‘3’ number of stones then another opponent will the game. If ‘Ale’ choosing the stones from ‘3’ number stone then ‘Bob’ will win and vice versa.
• If the number of stones is ‘4’ then ‘Ale’ will w...read more
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Q2. 
Return Subsets Sum to K Problem Statement
Given an integer array 'ARR' of size 'N' and an integer 'K', return all the subsets of 'ARR' which sum to 'K'.
Explanation:
A subset of an array 'ARR' is a tupl...read more
Ans. Brute Force
Recursively generate all the subsets and keep track of the sum of the elements in the current subset.
Subsets can be generated in the following way. For every element of the array, there are 2 options: 
1. Include the element in the current subset : If we include the element in the current subset, then we decrease the value of ‘K’ by  the value of the element.
2. Do not include the element in the current su...read more
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Round duration - 60 minutes
Round difficulty - Medium

This round was a video call round held on Zoom and the Codesignal platform was to be used for coding the problems. The round started with the interviewer giving a small introduction about him and then asking me to introduce myself.

Q1. 
Rotting Oranges Problem Statement
You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:
• 0 - representing an empty cell
• 1 - representing a fre...read more
Ans. Naïve Solution
The idea is very simple and naive. We will process the rotten oranges second by second. Each second, we rot all the fresh oranges that are adjacent to the already rotten oranges. The time by which there are no rotten oranges left to process will be our minimum time.
 
In the first traversal of the grid, we will process all the cells with value 2 (rotten oranges). We will also mark their adjacent cells ...read more
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Q2. 
Find Indices for Local Minima and Maxima
Given an integer array arr of size N, your task is to determine all indices of local minima and local maxima within the array. Return these indices in a 2-D list, ...read more
Ans. Brute Force
The idea is to iterate through the given array and at each index i, we check its neighbors to check if it's local minima or maxima.
 
Steps:
 
• We create two lists namely minima and maxima, to store all the indices of local minima and local maxima respectively.
• First, we check for the local maxima and minima conditions for the first element.
• Then we iterate through the given array from index 1 to N - 2, a...read more
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Round duration - 60 minutes
Round difficulty - Medium

The setup was exactly similar to the first interview round. The interviewer was very friendly. My advice will be to see the interviewer as a team mate and think you have to solve the question together with him. Don't panic and start speaking out what observations you can make about the problem.

Q1. 
Sort By Kth Bit
Given an array or list ARR of N positive integers and an integer K, your task is to rearrange all elements such that those with the K-th bit (considering the rightmost bit as '1st' bit) eq...read more
Ans. Iteration
The idea is to simply iterate through the ‘ARR’ and check each element whether its ‘K-th’ bit is 0 or 1, and add the element to the respective group.
 
Here is the algorithm:
 
1. Create an array/list ‘TEMP_ARR’ of size = ‘N’ for storing all the elements whose ‘K-th’ bit is 1.
2. Initialize a variable ‘j’ = 0 to iterate through ‘TEMP_ARR’.
3. Initialize a variable ‘p’ = 0 to iterate through ‘ARR’.
4. Run a loop from 0 ...read more
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Round duration - 60 minutes
Round difficulty - Medium

It was already night time till this interview started because all the three interview rounds were held on the same day. This was not a DS+Algorithms round. He first asked me to introduce myself. So I started by telling what all I have done in my college up till now and then I told him about my internship experience at myKaarma which just ended few days back. There was around 10-15 minutes discussion on what I was working on in my intern project.