# Ten in the bed

It’s been a while. And yes, I still have to write that follow-up post on the Project Euler problem “Maximum path sum”. I just didn’t work on it anymore. M.u.s.t.n.o.t.g.i.v.e.u.p!

Today’s short post will be on a much lighter note, namely a childrens’s song.

My little boy, two and half years old, loves to watch clips on YouTube. Almost every evening we move over to my little man cave and browse for car cartoons. Fire engine, ambulance, police car….all the stuff that he currently enjoys a lot.

We also watch a lot of children’s songs. “Wheels on the bus” anyone?

Yesterday I was struck by a little song called “Ten in the bed”.

There were 10 in the bed
And the little one said
“Roll over, roll over”
So they all rolled over
And one fell out

There were 9 in the bed
And the little one said
“Roll over, roll over”
So they all rolled over
And one fell out

There were 8 in the bed
And the little one said
“Roll over, roll over”
So they all rolled over
And one fell out

[…]

There were 2 in the bed
And the little one said
“Roll over, roll over”
So they all rolled over
And one fell out

There were 1 in the bed
And the little one said
Good night!

I’ve heard this song so many times without realizing that those lyrics are actually all about recursion.

So once my little one went to bed, I fired up my IDE and checked if I know at least a little bit about recursion, enough to hack the song in a couple of minutes.

Et voilà….

This is a very simple problem though.

A little while ago my boy and I started playing a boxed game. A car, a plane, a train and a ship travel through Europe on a map. We don’t follow any rules, just move the pieces along the roads, that connect Europe’s largest capitals.

Like the children’s song this sparked my interest. “How many different routes do exist?” “Can we visit all cities and use each road only once?”

I also remember to have a similar Sam Loyd puzzle somewhere in my bookshelf.

I might turn this into a blog post as well. But first a lot of reading has to be done and also the open Project Euler problem has to be ticked of my list.