The rules for writing programs are similar to contest rules. A brief resume: the program reads the test inputs from the standard input and places the results in the standard output; they don't need (in fact, they aren't allowed to) open files or to execute some system calls.

NOTE: To help some people, the Online Judge defines always the 'ONLINE_JUDGE' symbol while compiling your program. Thus, you can test for it to redirect the input/output to a file except while the Online Judge is testing your program. The following C example reads the input from a file called myprog.in and writes the output to myprog.out using only scanf() and printf(). The Online Judge will skip the open() and close() functions and will automatically use stdin and stdout instead of the files:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
                
main()
{
  int number;

#ifndef ONLINE_JUDGE
  close (0); open ("myprog.in", O_RDONLY);
  close (1); open ("myprog.out", O_WRONLY | O_CREAT, 0600);
#endif

  scanf  ("%d", &number);
  printf ("%d\n", number*number);
}

      If you already are a member (a registered user) and thus you have your own User ID, you can send by E-mail your C/C++/Pascal sources, solving any of the problems available in our database, to judge@uva.es, in order to test whether they reach a correct answer or not. For example, under Unix, and being p.c your solution for a problem in our Problem Set:

$mail judge@uva.es < p.c

      Your program must contain a line (at any location) with a @JUDGE_ID field. Usually, this line is placed inside a comment. For example, using C languaje (comments in C are placed inside /* and */) :

      The first field after the @JUDGE_ID: is your User ID (1000AA in the example). It is followed by the program number (100 in the example), and, optionally, by the languaje used (it may be C, C++ or Pascal). Don't worry about upper or lower cases. If you don't specify the languaje, the judge will try to autodetect it.

      If you have used any special algorithm or method, you can optionally include it between quotes (Dynamic Programming in the example): be careful in typing, and do not use more than 63 characters: it will appear in some Web Ranklist's. Please: don't place the problem title in the algorithm field (this will be redundant in the ranklists!).

      If your mail system adds extra lines at the end of your letter, you'll get a compile error. A way to skip this problem is to place a "@END_OF_SOURCE_CODE" or a "@end_of_source_code" message just after the last line of source code (also, you can place it inside a comment, but the entire message must be kept in a single line).

Notes:

• The source mustn't take more than 40,000 characters!   (please, contact us if you really need to send a bigger program).
• The source mustn't use more than 1000 characters per line.

      This method eliminates the E-Mail restrictions in file sizes or line length. And is faster. A short tool written in a few C lines (easy to be compiled) will do the job. This feature will be added soon!.

Back to Contest Problem Set