Programming Challenges – LC-Display re-judged

Wow – one of the problems that caused me grief on the programming challenges web site was 110104 LC-Display. Today when I logged in I noticed it was now marked as solved, yet I haven’t submitted that problem for 3 years. It also appears that I had 5 different correct solutions, that were originally marked wrong.

So someone has reviewed that problem, and found the judge solution was wrong, and re-evaluated all submissions. It’s good to see the site is still alive.

Pity they don’t have a forum as this was a good place to discus tricky problems, and give clues for the easier problems.

My 110206 Erdös Numbers solution is now showing as Compilation error (for all 160 submissions), so I might try and track that down…

Programming Challenges:110502 Reverse and Add

I solved the 110502 Reverse and Add problem today. The hardest part was whipping up the worker functions to do text based numbers.

I started by laying out the algorithm in function blocks, then proceeded to full in the gaps. I had two bugs

  1. my is_palindrome function didn’t have a default return value. It was C++ but even that seems a bit broken, but it compiled!
  2. my data structure could hold 10 digits (ie 1,234,567,890) as the problem stated, but that didn’t seem enough. Size 100 fixed that.

I haven’t done any simple problem work for a while, and I like the idea of doing some of the Rudy Quiz (albeit in C#), yet the testing structure of Programming Challenges site makes it a contained experience.

Programming Challenges Problems

Here’s the list the 21 problems I’ve solved on the Programming Challenges site.
If any ATR people have solved more I’ll have to start solving them again…

110101 The 3n+1 problem
110102 Minesweeper
110103 The Trip
110106 Interpreter
110107 Check The Check
110108 Australian Voting
110201 Jolly Jumpers
110202 Poker Hands
110203 Hartals
110207 Contest Scoreboard
110301 WERTYU
110306 File Fragmentation
110308 Fmt
110404 Longest Nap
110405 Shoemaker’s Problem
110406 CDVII
110504 Ones
110805 Tug of War
110903 The Tourist Guide
111302 Rope Crisis in Ropeland !
111308 How Big Is It?

The problems I can’t/haven’t solved and would love to hear of solutions for are

110104 LC-Display (edit 2008: now solved)
110206 Erdos Numbers (edit 2010: now solved)
110208 Yahtzee (edit 2010: now solved)
110307 Doublets
110801 Little Bishops
110804 Servicing Stations
111002 The Necklace

[Edit 2010] I have a newer, complete list here

Programming Challenges

Was reading Marks July 15 post, and remembered about my Programming Challenges time. Back in November 2004 I found the site, and start solving the problems. I shared the site with the people at ATR and some internal competition started. The site also had a phpBB attached, where people would ask questions and nobody would answer. So I decided to be the person that at lest acknowledge the persons question even if I did not know the answer. Most questions could be answered by repeating the answer given the day before. I am not sure if it was the new user base that just didn’t understand the concept of search before ask. The more annoying thing was there were problems with the problems, like solutions that worked on the bigger UVA site. The sites phpBB was pulled done earlier this year due to it been hacked, and has not been replaced. The site admins never answered any questions, so it would appear to just be a pretty version of the UVA site, to help sell their book. I’ll admit the site gave you the error output when you code fails to compile which UVA does not. The small problem set also makes the site less intimidating.

While the phpBB was still active I was discussing the above problems another coder, who suggested TopCoder, describing it as having good feedback, and the chance to win money. So I promptly signed up there and never did anything about it.

So last week I entered my first algorithm competition, man it was fun. It was a session sponsored by the NSA, so they had a few people in the chat room for an hour before the competition. The competition it’s self was fun. The third problem was simpler than I first thought so I wasted a lot of time thinking I couldn’t do it. Then added extra code that wasn’t needed. So now I’m in Division I, and the problems look a lot hard. You start in Division II when you are unranked. I’m keen to compete in the next competition that happens in my time zone on the 8th. This one has cash prizes, but I’m not expecting to get any. Here the my TopCoder profile in case you feeling competitive ATR people.