Archives for May 2015

You can read a lot on Quora about the best language to use for competitive programming. Here are some of the points covered by those questions:

• C and C++ execute quickly, and their macro support can reduce the amount of code that you end up typing in your solution.
• A language like Java can be useful for problems with some specific requirements (such as integers that don’t fit in 64 bits, or calendar problems).
• The main contributor to execution speed is the algorithm that you use, not the language that you choose to implement it. But the language can provide a performance edge at the margins.
• Choice of language is less important for more recent contests, since problem setters have made an effort to level the playing field (e.g., by testing Java solutions to ensure that the time limit is sufficient).

I decided to use Java for Project 462, mainly because it’s similar to my primary language (C#), and I’m more interested in learning about problem solving and algorithms than learning a new language that I’m unlikely to use much outside of competitive programming.

One thing about the uHunt problems that I’m working through is that they draw from a database of contest problems going back to the 1990s. Competitive programming and programming languages have changed a lot since then, so what the problem setters were going for in the original contest may not match up with how a contestant sees the problem today. Modern contests tend to be more forgiving of the slower execution time of languages that aren’t C or C++, and they know about the fancy libraries that programmers have access to.

Last week I wrote about Solving UVa 11340 in Java, and covered some performance tips related to reading files that are larger than those typically found in programming puzzles. It turns out that the very next starred problem, UVa 12356: Army Buddies, is an even stricter test of I/O performance. And for this one, there is no particular hint in the problem statement that I/O will be an issue.

Once I came up with an Accepted solution for UVa 12356 in Java, I decided to do some more benchmarking, and use the results to update my solution template. Figuring all of this out once is educational, but I’d rather not be fiddling with I/O issues for every problem that happens to have large input or output requirements.

« Continue »

UVa 11340: Newspaper, despite being ranked at only Level 2 difficulty on uHunt, turned out to be rather tricky. Apparently others thought so too, judging by the 11 pages (151+ posts) of discussion on the UVa OJ message board. Many of the message board posts focus on the characters used in the test input. The consensus is that they are 8-bit characters (with values from 0 to 255). At a minimum, these characters need to be stored in an unsigned char data type in C++. Nevertheless, people seemed to run into problems even after getting that hint. I solved the problem in Java, which doesn’t have an unsigned char data type, but it has its own set of difficulties. I’ll cover the two issues that I ran into when solving this problem.

« Continue »