Winter Bash 2019

I’ve been very busy with work for the past six months, so I haven’t been blogging.

Stack Exchange Winter Bash 2019 ends tomorrow.  I was able to get five hats, and a bug let me wear (but not own) a sixth hat early.  My heavy work schedule as well as recent events on Stack Exchange have resulted in my not being so active in getting more hats.

ACM ICPC Philippines Southern Luzon Invitational Programming Contest 2018

For the sixth time in a row, I was a problem setter and judge for an ACM ICPC programming contest held in Ateneo de Naga University.  Last October 7, 2018, twelve teams participated and their performances are shown below.  I guess the low number of participants is due to the two-year absence of new undergraduate students (from 2016 to 2017) due to the addition of two years of senior high school in the Philippine educational system.

I contributed two problems:  Problem C: “Symbolic System” (based on the symbolic system described on page 102 of Wolfram’s “A New Kind of Science”) and Problem E: “Fibonacci Ones digit” (based on Rossi D’Souza’s “Where did/do mathematical concepts come from?” in For the Learning of Mathematics, vol. 36, no. 1, pp. 25-27).  Only two teams attempted problem C; only one team attempted problem E; all three failed to solve the problems.

2017 ACM-ICPC Philippines Southern Luzon

I was a problem setter and judge for the 2017 ACM-ICPC Philippines Southern Luzon Invitational Programming Contest held last October 1, 2017 at the Ateneo de Naga University. Seven teams from five schools joined, which is much less than the numbers in the previous years (15 teams from 9 schools in 2016, 13 from 6 in 2015, 31 from 13 in 2014, 32 from 15 in 2013). The contest problems and solutions are here. I provided two contest problems: “C” (Sharkovski Successor) and “D” (String Substitution). I was also a problem setter and judge in 2016, 2015, 2014, and 2013.

It’s your watch

I had been planning to buy a digital watch for some time, something metal like the A158WA-1 or the A159WGEA-1EF. I really wanted to get an A159WGEA-4AEF but all I kept seeing in the stores were A159WGEA-9AEF.

But when I saw this Casio F-91W Gold, I bought it immediately. The black resin strap is quite thin, and with regular use, I expect it to last only a few years. From the back you can see that the body is made of metallic beige plastic and it seems that the front has a thin piece of gold-colored metal covering it. It seems that this model is also available with the metal colored silver.

Some time ago, Seiko had an advertising campaign that stated “You can tell more about a person by the watch they wear than anything else” and “It’s your watch that tells most about who you are.” This F-91W gold is simple and special, just like me.

2016 ACM-ICPC Philippines Southern Luzon


I was a problem setter and judge for the 2016 ACM-ICPC Philippines Southern Luzon Invitational Contest held last October 1, 2016 at the Ateneo de Naga University.

The winning team was from the University of the Philippines, Los Baños. It solved 7 of the 12 problems. (The teams were given 5 hours.) The results are shown below. (The image has been slightly edited.)


If I’m not mistaken, the warm-up problems were the same as last year’s.  The contest problems are here. I provided two contest problems: “C” (Billiard Paths 1) and “H” (Billiard Paths 2).  (My slides explaining my solutions are here and here.) As you can see from the scoreboard below, two teams attempted problem “C” (and both succeeded), and no team attempted problem “H.”


I was also a problem setter and judge in 20152014, and 2013.