In Competitive Programming, most of the time we need to enter input for checking our code manually. But it would become cumbersome if we have a questions like Graphs, strings, or bulky entry of input data because it will definitely time out or the chances of typing incorrect data would be increased.
We can easily get rid of problem by simply saving the test cases to the specified file at the desired location according to our easiness. These are useful in competitions like Facebook Hackercup, Google Codejam. These competitions do not provide the online judge like environment rather than they asked you to upload input and output files.
For Input/Output, we basically use these two type of file access modes i.e.,
- “r”: It means read, as it opens the file for input operation but the file must exist at specified location.
- “w”: It means write, as it creates an empty file for output operations. If a file with the same name already exists, its contents are discarded and the file is treated as a new empty file.
In C/C++ we can use freopen for standard input and output. The syntax of this function as:-
FILE * freopen(const char * filename, const char * mode, FILE * stream );
- filename: It refers to name of the file that we want to open.
- mode: Discussed above.
- stream: Pointer to a FILE object that identifies the stream to be reopened.
We can also use Symbolic constant ONLINE_JUDGE for debugging purpose. As most of the online judges add this flag at the end of the command line before executing our code. For example in C++11, it would be compiled as
-std = c++0x -O2 -static -s -lm -DONLINE_JUDGE
So we can take advantage of that by using C preprocessor directive.
- FileReader(String filename): This constructor creates a new FileReader, and instructs the parser to read file from that directory. The file must exist in that specified location.
- FileWriter(String fileName): This constructor creates a FileWriter object, to the specified location.
In python we first import the module sys(system), after that We will use open() function which returns the file object, that are commonly used with two arguments: open(filename, mode).
- The first argument is a string containing the filename.
- The second argument is another string (mode) containing a few characters describing the way in which the file will be used.
This article is contributed by Shubham Bansal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
- Top 10 Algorithms and Data Structures for Competitive Programming
- How to begin with Competitive Programming?
- How to become a master in competitive programming?
- Tips and Tricks for Competitive Programmers | Set 1 (For Beginners)
- Tips and Tricks for Competitive Programmers | Set 2 (Language to be used for Competitive Programming)
- Competitive Programming: Conquering a given problem
- Fast I/O for Competitive Programming
- A Better Way To Approach Competitive Programming
- getchar_unlocked() - faster input in C/C++ for Competitive Programming
- Bitwise Hacks for Competitive Programming
- Some important shortcuts in Competitive Programming
- Quick ways to check for Prime and find next Prime in Java
- Fast I/O in Java in Competitive Programming
- Formatted output in Java
- Frequency Measuring Techniques for Competitive Programming