Facebook Software Developer Intern Interview Questions, Process, and Tips

The first round comprised of 4 sections online questions including aptitude, logical, Coding questions, and technical portions (Test Duration: 90 mins):

Debugging: We had to choose a language and debug up to 7 questions most probably. Codes were very basic like sorting, etc. I completed 6 of them.

Coding: There were two medium-hard level questions.

Work-style Assessment: Just try to answer as an ideal employee. Make sure you answers don’t contradict each other.

Aptitude: Around 25 questions.

Q1. Find diameter of tree
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Q2. Count inversion
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Q1. Find n’th node from the end of a Linked List
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Q2. Find shortest distance between 2 points in a matrix, where 2 points can be anywhere
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This round had first questions about behavior, team work and hr type mcq questions.
Then there were 10 computer science mcqs. Then two coding questions.

Q1. This was of 1 hour. He asked about 2-3 dsa questions and some hr questions in last part.
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Q1. This was also a similar round like round 2. In this he asked 2 medium dsa questions and some hr questions at last.
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Easy Questions- Can be done with decent practice

Q1. Array question - basic knowledge sufficient
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Q2. Maths questions + stack implementation
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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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