Just a hint, so you don’t go down the wrong path. You probably won’t, but if you don’t want any hints, stop reading this article!

PS If you don’t know what Project Euler is, I recommend having a look at their website, or just getting an idea from the problems themselves.

What is Project Euler?

Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.

Now problem / puzzle 11:

In the 2020 grid below, four numbers along a diagonal line have been marked in red.


The product of these numbers is 26 63 78 14 = 1788696.

What is the greatest product of four adjacent numbers in any direction (up, down, left, right, or diagonally) in the 2020 grid?

Just a hint for those of you who spent too long on this like me: it’s essentially a word search. One of these but with numbers.

You see, when I got the wrong answer a couple times I reread the question, and figure “adjacent” just meant anywhere beside each other – eg a square of four numbers, a t-shape. This is not the case! You don’t need to develop a path-finding bot that navigates 4 numbers, looking for the best options! Although, having done that, it’s actually quite fun! In python, at least, it’s quite concise and the code is pretty-looking.

Bonus points (or a packet of chocolate-coated raisins) to the first person who does implement such an algorithm. The answer I’m looking for is the highest product of the resulting 4 numbers, and leave it in the comments.

Bet I won’t get an answer!