Solving seemingly simple math problems using Perl
5x5 Test Run
The sought-after groups in the math puzzle can now be put together very easily from this megasquare in a way that avoids overlap between participants on several consecutive days. Because these are only 5x5 squares, the method can only generate five groups each with four (n-1) participants for five days: one teacher (of a total of five), one male student (also of five) and two female students (out of 10). Figure 7 shows the result, which is practically just a simple transformation of the entries from the megasquare in Figure 6.
The script in Listing 1 [5] moves from left to right and from top to bottom through the entries and translates them into people. The entry 1111
thus becomes i1 b1 g1 g6
, because it relates to the first teacher, the first boy, the first girl from the first group, and the first girl from the second group. The entry 3524
accordingly becomes i3 b5 g2 g9
, and so on.
Listing 1
combi-prime
That's How to Do It
But, how does the script initially generate the four orthogonally arranged Latin squares from which the group arrangement can then be easily derived? The process is pretty simple, as it concerns 5x5 squares and five is a prime number.
Trust Is Good
The x and y values printed in black along the edges of the squares in Figure 5 run from 0 to 4 and are in mixed-up order (0,2,3,4,1), because order does not matter to the algorithm. Each element of the matrix is computed by the simple formula (ay+x) mod 5+1, where a is set to 1 for the first square, to 2 for the second, and so on.
This process results in the following value for the element that is in the second column of the third row of the fourth square: The y value of the third row of the fourth square is 3, the x value of the second column is 2, and the value for a in the fourth square is 4, this returns 4x3+2=14. Reduced to modulo 5, 4 is left over, then 1 is added – because the sequence of values is from 1 to 5, not from 0 to 4 – giving a final result of 5.
Listing 1 implements this formula in the for
loops from line 14 and then starts outputting the combinations in the final part from line 37. The whole thing executes very quickly because the calculations are simple and the algorithm is linear, without any form of backtracking.
« Previous 1 2 3 Next »
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
TUXEDO Computers Unveils Linux Laptop Featuring AMD Ryzen CPU
This latest release is the first laptop to include the new CPU from Ryzen and Linux preinstalled.
-
XZ Gets the All-Clear
The back door xz vulnerability has been officially reverted for Fedora 40 and versions 38 and 39 were never affected.
-
Canonical Collaborates with Qualcomm on New Venture
This new joint effort is geared toward bringing Ubuntu and Ubuntu Core to Qualcomm-powered devices.
-
Kodi 21.0 Open-Source Entertainment Hub Released
After a year of development, the award-winning Kodi cross-platform, media center software is now available with many new additions and improvements.
-
Linux Usage Increases in Two Key Areas
If market share is your thing, you'll be happy to know that Linux is on the rise in two areas that, if they keep climbing, could have serious meaning for Linux's future.
-
Vulnerability Discovered in xz Libraries
An urgent alert for Fedora 40 has been posted and users should pay attention.
-
Canonical Bumps LTS Support to 12 years
If you're worried that your Ubuntu LTS release won't be supported long enough to last, Canonical has a surprise for you in the form of 12 years of security coverage.
-
Fedora 40 Beta Released Soon
With the official release of Fedora 40 coming in April, it's almost time to download the beta and see what's new.
-
New Pentesting Distribution to Compete with Kali Linux
SnoopGod is now available for your testing needs
-
Juno Computers Launches Another Linux Laptop
If you're looking for a powerhouse laptop that runs Ubuntu, the Juno Computers Neptune 17 v6 should be on your radar.