Hacking Challenge: Christmas visits nightmare!

I originally wrote this challenge in 2012 to select a few developers for my previous company. They turned it down! I still think it's a nice puzzle. I would like to publish more in the future, let's see how this goes.


Subsitute //Write code here... with your awesome solution. Feel happy.

If you want me to look at it, your answer to [email protected] (if you can't guess the email, there's a captcha waiting for you as a punishment). If you don't want me to look at it, that's ok, too. This is not a competition, but a past time.

Next week I'll publish a solution.

The Challenge

happy holiday

You have a very large family, and it seems that everybody wants to visit this Christmas! Unfortunately, you only have one guest room, so you can't accomodate more than one relative at any one time, but, since you love all your relatives equally, you want to get to see as many of them as possible.

Write a method which returns a list of relatives that lets you see most people without overlaps. Results are ordered by start date.

public IEnumerable<Relative> ScheduleVisits(IEnumerable<Relative> visitRequests) 
    //Write code here... 

//Example input:
var input = new[]
        new Relative {Name = "Aunt Alice", Start = "21-12-2012", End = "24-12-2012"},
        new Relative {Name = "Uncle Bob", Start = "23-12-2012", End = "26-12-2012"},
        new Relative {Name = "Cousin Charles", Start = "26-12-2012", End = "27-12-2012"},
        new Relative {Name = "Grannie Delia", Start = "24-12-2012", End = "25-12-2012"}

//Example output:
var output = new[]
        new Relative {Name = "Aunt Alice", Start = "21-12-2012", End = "24-12-2012"},
        new Relative {Name = "Grannie Delia", Start = "24-12-2012", End = "25-12-2012"},
        new Relative {Name = "Cousin Charles", Start = "26-12-2012", End = "27-12-2012"}

There are two things I'd like to add: there is at least one edge case which is not included in the sample data. Can you identify it? Can you determine the big O of the algorithm you are producing? Can we make it better?

Hi, I'm Marco Cecconi. I am the founder of Intelligent Hack, developer, hacker, blogger, conference lecturer. Bio: ex Stack Overflow core team, ex Toptal EM.

Read more

Newest Posts

Guest blog: Building, in partnership with communities by Shog9

A lesson in building communities by Stack Overflow's most prominent community manager emeritus, Shog9

Read more
Can you migrate a company from on-premise to remote-only?

Some lessons learned over the past 8 years of remote work in some of the best remote companies on the planet

Read more
Announcing Intelligent Cache, our caching library

Our newest open source initiative, intelligent cache, is available for use

Read more
Guest Blog: The mythical 10x programmer by Antirez

In this post, Salvatore Sanfilippo puts together a list of qualities that I believe make the most difference in programmers’ productivity.

Read more

Today I want to introduce our second engineering team: Team EMEA

Read more


And the Most Realistic Developer in Fiction is...
Julia Silge • Mar 28, 2017

We can say that Mr. Robot is having a moment. The main character was one of the top choices and thus is perhaps the most/least realistic/annoying/inspiring portrayal of what it’s like to be a computer programmer today.

Read more…