Running Code Locally

C++

Java

It can be useful to use a Java IDE to take advantage of the powerful debugging features in Java.

Python

Python comes with a program, known as IDLE (Integrated Development and Learning Environment), that allows one to write and run Python code. It supports many features, such as syntax highlighting and automatic indentation, that one would normally expect from an IDE/text editor. However, feel free to use another editor or IDE if you want to.

C++

You can run your C++ programs from the command line and use a text editor of your choice.

Text Editors

Vim is probably the easiest way to print syntax-highlighted code on Mac, see the response to this post.

Sublime Text Notes (Ben)

• I prefer the Mariana color scheme in place of the default.
  • open command palette (Cmd-Shift-P) -> change color scheme
• subl symlink
  • Using /usr/local/bin/subl instead of ~/bin/subl worked for me on OS X Mojave.
• Package - Sublime Linter (GCC)
  • highlights compilation errors and warnings from -Wall
  • can change compilation commands in linter.py
• Package - Fast Olympic Coding (I don't use)
  • test manager can be useful
  • linting is covered by the above
  • stress testing is covered in Debugging
  • can't get debug to work

Further Instructions

See this module for information about installing, compiling, and running C++ from the command line.

Including <bits/stdc++.h>

You can use #include <bits/stdc++.h> in place of separately including libraries.

Usage

This is usable with GCC. However, Mac OS X uses Clang while Windows uses Microsoft Visual C++ (MVSC) by default. <bits/stdc++.h> is not a standard header file, so it will not work with the latter two. This is one of the reasons why you should not use <bits/stdc++.h> outside of competitive programming.

If you install GCC as described later in the module linked above, then you should be good to go.

OS-Specific Recommendations

Linux

Windows

Geany or CodeBlocks?

Mac

XCode?

Using <bits/stdc++.h> Without Installing GCC

If you installed Clang on Mac, then you can download stdc++.h from here and move it into a folder named bits that is located in the same directory as where all other C++ header files are located. However, this is not recommended.

Java

First, download the JDK. Then, test that you can use the right commands.

On Windows, open cmd and type the following command into the prompt:

java

If you get the below result, you may have to add the JDK to your PATH variable.

'java' is not recognized as an internal or external command,
operable program or batch file

Otherwise, you're probably good to go.

Compiling and Running

Running a Java file off of the command-line is relatively simple after the JDK is downloaded.

Consider this code of Main.java and assume it is in a file on your computer:

1public class Main {
2    public static void main(String[] args) {
3        System.out.println("Hello World!");
4    }
5}

Use the cd command on your console to get to the directory that contains Main.java. Then, run the following command to compile the code:

javac Main.java

If it runs successfully, a file called Main.class will show up in the same directory, which can be executed with the next command:

java Main

If everything goes accordingly, the console should output Hello World!.

If you do USACO-style file I/O, meaning that files are in the "local directory", then the files must be located in the same directory as the source code (if you use the above method).

Python

Download Python through the official website. On Windows and Mac, you can download executable files directly; on Linux, you must either download the Python source code and compile from source, or obtain Python through your package manager.

Make sure that you are using the correct version of Python. Python 2 is quite different from Python 3 (but parts of the version number beyond 2. or 3. do not matter much). We generally recommend newcomers to use Python 3, but if you are used to programming in Python 2, that is OK too.

The Python version can matter when using the command line to run Python; sometimes, python3 must be used instead of python in order to run Python 3. Try both commands, and pay attention to the version that Python prints to determine if this is the case on your system. For example, running the following in Terminal on my computer produces:

python --version # prints Python 2.7.13
python3 --version # prints Python 3.8.1