# CommonFloor Interview Experience | Set 1 (Placement Questions 2014)

Company : commonfloor.com (MaxHeap Technologies)

Criteria : Open to CSE , EE , EC , MA ; No CGPA Criteria

**Qualifier Round: on hackerearth.com**

1 hr 30 min : 5 Objective Questions and 1 Coding Question.

1) Definition of Foreign Key (DBMS).

2) No. of colors needed to colour any Planar Graph

3) Minimum Hamming Distance to detect error ….

4) No of nodes in a complete binary tree of height h

5) Equality of two regular expressions (Identity based).

Coding Question :

You are given the vertices , edges , start vertex and end vertex of a

graph .The graph is directed and can have loops .Each edge is of length 1 . You task is to find the min distance b/w start and end vertex if it is reachable , else print (-1)*(#Vertices reacheable from start vertex)

#Vertices <= 100000 #Edges <= 100000

BFS is obvious .Only thing is that Graph must be implemented as Adjacency List rather than Adj Matrix else it causes Memory Limit Exceeded error.

**Tech Interview Round 1: (Approx 1 hr)**

1) Problem Statements of N Queens Problem , Sudoku Problem and strategies for solving them

2) Problem Statement of Tower of Hanoi , Write Code to solve it and extended it to 4 towers

3) Sort an array of zeros and ones

4) Find the first non repeating element in an array and Various Approaches (Like No additional

mem , one traversal)

5) 25 horses - Minimum Races Puzzle

6) Find all the triplets from an array that sum to a given number.Report their indices.

Discuss various approaches like naive , sorting etc..

7) Problem which can be mapped to Finding maximum Lexicographical subsequence from a string.

**Tech Interview 2: (Approx 1 hr)**

OS Funda :

1) Def of Process , Threads , their diff ,Multi Threading and a discussion about them

2) What is Virtual Memory and discussion on Memory Management techniques

3) What is Race Condition? What is Shared memory ?

4) What is Critical Section ? Peterson sol?

5) 2 Processes and their codes are given . (Indirect )Find the Critical Section

Android (I had my intern and BTP on Android ):

1) General discussion abt Android app that I did and my project

2) Activity Life Cycle and diff methods

DBMS :

1) Indexing and types

2) Primary Index and Composite Index

3) Discussion about SQL

ALGO :

1) Find whether a string is a substring of another .[I tried KMP but ended up explaining the Naive Approach].

2) Discussion on why my code didnt pass all test cases ==> Ways of representing a graph , pros and cons of diff ways, Several situations and suitable rep of graphs.

3) Question which can be mapped to finding Longest Common Subsequence. Write Complete working Code.

4) Basics of Binary Search Trees , Defined a new bst with an additional attribute size (sum of nodes of left child , right child + 1). Find the Kth smallest node . Explain and write working code {Time Constraint : 2 min }

**HR Interview : (2 HR ppl , Appprox 1/2 hr )**

1. Introduce yourself , What do you know abt Commonfloor , Why do you want to join?

2. Suggest Some changes and also new features to add to Commonfloor website .

3. Detailed Discussion about my internship

# How did I develop the ecommerce application ?(Like division of work , Coordination of work, Asked me to show the app live on my Phone !!!!)

# Discussion abt Apache Cordova vs Android { Basically it was like my talk }

4. Discussion about my B Tech Project (about Power Consumption by Android Applications) and basic questions about Gantt Chart and Gantt Project (Part of my BTP)

5. Questions about my DBMS Academic Project "Carpooling" .Enhance it into a business model leading to maximum profits (I told features to make it better and the other business that can be created from Carpooling data)

6. Personality Questions like "Tell me one quality why I should hire you ?" , "Your quality which you dont like the most"

My Turn: I asked about work culture , timings , etc..

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