This past Saturday, I spent the evening at a small party hosted by my colleague, Dr. Macdonald, at his new pastoral home, about an hour outside the city. During the course of the evening, obviously after exchanging pleasantries and congratulating him on his new domicile, I asked him what he was working on. He smiled cryptically and broke off the conversation, I thought I'd offended him, but yesterday he came into my office and dropped off a piece of paper containing only the following 24x15 grid of letters.


What is he trying to tell me?

  • $\begingroup$ You reposted, just to change JI to IJ? Why not just edit the old one? $\endgroup$ Sep 14, 2016 at 14:46
  • $\begingroup$ @randal'thor Oh, crap, I thought self-deletes before answers or votes were actually deletes. I found a spelling mistake in my creation notes, and thought an edit history for that particular change would be a non-minor spoiler. $\endgroup$
    – Sconibulus
    Sep 14, 2016 at 14:51

1 Answer 1


The answer is:

Researching search algorithms. Credit @Gareth McCaughan


On the grid we can find the following:
Dijkstra's - referring to Dijkstra's algorithm
Binary - credit @RosieF - referring to the Binary search algorithm
Depth - referring to the Depth-first search algorithm
First - added to depth and breadth to complete the algorithm names.
Grovers - perhaps referring to Grover's algorithm
Fibonacci - referring to the Fibonacci sequence / Fibonacci search technique
Breadth - referring to the Breadth-first search algorithm (@M Oehm)
Alpha, Beta and Pruning - referring to the Alpha-beta Pruning search algorithm (again diagonally).
Tree - diagonally. Could be added to Binary for Binary-tree search algorithm.
Neighbor appearing twice next to each other - referring to the Nearest neighbor search algorithm ( @Gareth McCaughan and @M Oehm )
Naive - referring to the Naïve String Search, Also mentioned on this wiki-page
Prims - referring to the Prim's algorithm (@M Oehm)

The repeating As, Bs and Ds (sequences of 5 each) could refer to A*, B* and D* search algorithms. The As and Ds also appear on the row above and twice on the row below the sequence, forming a star. - comment from the OP.

Something to help with the word searching: https://wordsearch.lukasjoswiak.com/p/8767172

enter image description here


There are long sequences of the same letter: There are 5 of As, Bs and Ds (as also noted above), and a sequence of 4 Gs.
There is also a sequence on the 14th row of all the vowels ordered alphabetically AEIOU.
Disclosed from the OP himself in chat: The name Macdonald refers to a famous song, where they sing "EIEIO".
Using this as a key in Vigenere cipher on the first 3 rows, we get:
i.e. "This isn't a cipher, although yku might think it looks a little bit like one"

  • 1
    $\begingroup$ Maybe the answer is simply that your colleague is researching search algorithms. Binary search, depth-first search, and Fibonacci search are all things; Grover's algorithm is a quantum algorithm for searching. I wouldn't personally call Dijkstra's algorithm a search algorithm, but I've seen it called that. (And of course what we're all doing is searching the grid.) Dunno about "place"; maybe it's a coincidence. $\endgroup$
    – Gareth McCaughan
    Sep 16, 2016 at 9:32
  • $\begingroup$ @GarethMcCaughan there is actually an "In-place algorithm". But it is not a search algorithm. So it could be just a coincidence... $\endgroup$ Sep 16, 2016 at 9:46
  • $\begingroup$ If you go southeast from the B at (4, 3), you can see "breadth". Breadth First and Depth First are ways to traverse graphs or binary trees. $\endgroup$
    – M Oehm
    Sep 16, 2016 at 9:56
  • $\begingroup$ @MOehm, yup. The reason I think that if we're on the right lines it's something broad like "search algorithms" rather than anything specific to graphs or trees is that Grover's algorithm is emphatically not for searching that kind of interestingly structured data; it just operates on an array. $\endgroup$
    – Gareth McCaughan
    Sep 16, 2016 at 10:28
  • 1
    $\begingroup$ There's also Prim or Prims (for Prim's algorithm) at (23, 9) and Naive (for any naive search) at (18, 9). Okay, so we're searching for search algorithms and the leftover letters don't look promising. Could the words in the grid form a kind of graph? $\endgroup$
    – M Oehm
    Sep 16, 2016 at 11:39

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