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

With the variety of software available for Windows, deciding what to use can be difficult. While the most popular options are Visual Studio Code, Geany, and CodeBlocks, any text editor or IDE that you feel comfortable using (as long as it works with C++) will work.

To get the full functionality of C++ on your Windows Machine, you should install one of the following compilers, from easiest to most difficult to set up and use:

Simple: MinGW (Minimalist GNU for Windows)

If you want to keep the ease of use and simplicity of Linux C++, including the ability to use commands like g++ and easily include <bits/stdc++.h>, you can install the compiler MinGW. This is a version of the g++ compiler from Linux available on Windows. If you are using VS Code, setting up MinGW can be more difficult, but there are great guides to make the process easier.

Depending on the installer you used, installing MinGW could be a little complicated.

The Official Installer:

1. First, download and run the MinGW installer.
2. Once it's installed, open the MinGW Installation Manager, click on Basic Setup on the left, and select mingw32-gcc-g++-bin for installation.
3. Finally, Add it to your PATH following the latter half of this tutorial

Microsoft's Mirror Installer:

1. First, download the installer
2. When you run it, leave all settings at default except Architecture.

   1. For Architecture, select x86_64.
3. After you click next, copy the Destination Folder Path for later and finish the installation.
4. Now, you need to add MinGW to your Path. To do that:

   1. After the Installation has completed, search for Environmental Variables in the Windows Search Bar and click open
   2. Click the button Environment Variables at the bottom left.
   3. In the bottom half of the screen (under System variables), find the key Path and double click.
   4. Click New on the top right and paste the path you copied. Add \bin to the end of it. It should look something like this: C:\Program Files\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\bin
   5. You're Good to Go!

Moderate: Microsoft Compiler Toolset

Microsoft's Visual C++ Compiler is the official compiler for compiling programs for Windows and can be installed either via installing the relevant packages with Visual Studio 2019 or the build tools from their website. More information on its installation can be found in their documentation.

In order to get a similar library to <bits/stdc++.h> you can use the following template, which automatically swaps between <bits/stdc++.h> and Microsoft's variant depending on the system running it:

#ifdef _WIN32
#include <__msvc_all_public_headers.hpp>
#endif
#ifdef __linux__
#include <bits/stdc++.h>
#endif
using namespace std;

This checks if the compiler is compiling for windows (your local machine) or if it is compiling for the remote judge and subsequently includes the correct libraries for the system. This comes with the same consequences as using <bits/stdc++.h> for the same reasons.

Note: As USACO has now disallowed the use of templates during competitions, if you want to be able to get the functionality of <bits/stdc++.h> on your local machine, you should use MinGW instead.

Difficult: Windows Subsystem for Linux (WSL)

If you're already accustomed to the Linux Command line, this might be the best option for you.

Windows Subsystem for Linux, commonly referred to as WSL, runs the linux kernel (or an emulation layer, depending on which version you use) within you windows installation. This allows you to use Linux binaries without needing to use Linux as your main Operating System, meaning that you can install g++, use g++, and consequently include <bits/stdc++.h> in your Competitive Programming C++ files.

Many people use WSL (such as Anthony), but it can be difficult to properly set up.

If you want to code in (neo)vim, you can install WSL and code through WSL bash.

To install the necessary tools after setting up WSL, you can run the following commands.

On Debian based distributions like Ubuntu:

sudo apt-get install build-essential

On Arch based distributions like Arch Linux:

sudo pacman -Sy base-devel

You can find many tutorials on how to style up WSL and make it feel more cozy. The first step is to use a proper terminal and not the default one that Windows provides. An easy to use option is Windows Terminal, which can be found on the Microsoft Store.

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

Installation

Linux

First, you can check if you have Java already installed by running java --version in the terminal. If it returns something like this:

openjdk 11.0.9.1 2020-11-04
OpenJDK Runtime Environment (build 11.0.9.1+1-Ubuntu-0ubuntu1.20.04)
OpenJDK 64-Bit Server VM (build 11.0.9.1+1-Ubuntu-0ubuntu1.20.04, mixed mode, sharing)

That means you have Java installed already. On the other hand, if you get something like this:

Command 'java' not found

You will have to download and install JDK. On most Linux distros, the JDK can be downloaded via the built in package manager.

Ubuntu/Debian

On Ubuntu, Debian, and other Ubuntu/Debian based distos, the JDK can be installed via apt. You can install the Java JDK from the default repositories by running: sudo apt install default-jdk.

After this finishes installing, if you run java --version again, you should get something like above.

Arch

On Arch and other Arch based distos (like Manjaro), the JDK can be installed via pacman. You can install the Java JDK from the default repositories by running: sudo pacman -S jdk-openjdk.

After this finishes installing, if you run java --version again, you should get something like above.

Fedora

On Fedora and other Red Hat based distos, the JDK can be installed via dnf. You can install the Java JDK from the default repositories by running: sudo dnf install java-openjdk-devel.x86_64.

After this finishes installing, if you run java --version again, you should get something like above.

Windows

First, can check if you already have Java installed by running java --version in cmd. If it returns something like this:

openjdk 11.0.9.1 2020-11-04
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.9.1+1)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.9.1+1, mixed mode)

That means that you have Java installed already. On the other hand, if you get something like this:

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

You will have to download and install JDK from here.

After it finishes installing, if you run java --version again, you should get something like above. Note: the installer should automatically add Java into the system PATH, but in the event that it doesn't, you can find more information on how to do that here.

macOS

First, can check if you already have Java installed by running java --version in the terminal. If it returns something like this:

openjdk 11.0.9.1 2020-11-04
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.9.1+1)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.9.1+1, mixed mode)

That means that you have Java installed already. On the other hand, if you get something like this:

-bash: java: command not found

You will have to download and install JDK from here.

After it finishes installing, if you run java --version again, you should get something like above.

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:

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

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). You can find a Java testing script for USACO here.

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