Adding Solutions

Authors: Nathan Wang, Benjamin Qi, Qi Wang

Contributors: Maggie Liu, Sathvik Chundru

How you can add your own solutions to the guide.

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See Working With MDX for additional information.


  1. Fork the GitHub repository.

  2. If it doesn't already exist, create a new mdx file in solutions/ including frontmatter, e.g. the following in usaco-690.mdx:

    id: usaco-690
    source: USACO Silver 2017 January
    title: Cow Dance Show
    author: Óscar Garries
    [Official Analysis](
    ## Explanation
    (add explanation here ...)
    Use `\texttt{}` around variable names with length *greater than one*, like so. Place long equations on separate lines with display math, and use `\cdot` instead of `*` to denote multiplication.
    \texttt{arr}[i]=2\cdot (a+b+c+d+e)+\sum_{j=0}^{i-1}\texttt{arr}[j]
    Some additional text styles which you might consider using:
    ## Implementation
    **Time Complexity:** $\mathcal{O}(N\log^2N)$
    ^ Format time complexity like this. Should appear outside of `<LanguageSection>` if it's the same for all implementations.
    (add cpp code)
    (if you have Python code)
    (if you have Java code)

    Keep file names and solution IDs consistent. In particular, the ID for a USACO problem (such as the one above) is the number at the very end of the URL on The name of a solution file should match the ID of the solution it contains. See Working With MDX for more examples of IDs.

  3. Add your implementation, following these conventions below. It is not necessary to add an alternative implementation in the same language as the official implementation unless the alternative implementation takes a different approach or is better than the official one.

  4. In the module's .problems.json file (in this case, Binary_Search.problems.json), change the kind of the solutionMetadata field to internal and remove all other fields. Also add tags (if you want). If the problem is not in a module, you can add the problem to extraProblems.json.

      "uniqueId": "usaco-690",
      "name": "Cow Dance Show",
      "url": "",
      "source": "Silver",
      "difficulty": "Easy",
      "isStarred": false,
      "tags": ["Binary Search", "Ordered Set"],
      "solutionMetadata": {
        "kind": "internal"
  5. Check that both the module and the solution render properly using the live editor before submitting a pull request.

Code Conventions

Since code for the USACO Guide is contributed from several authors, code style will not be uniform. Of course, we still strive for code that is readable and understandable. If any code does not compile or is hard to read, contact us.

Read our guidelines below before contributing code.


  • In general, do not include unused code (e.g. "templates").

    • There are some exceptions to this guideline (e.g. when using the Kattio class for Java I/O). In this case, collapse it with a CodeSnip.
  • Use tabs rather than spaces to indent.

    Pro Tip

    If your code is indented with spaces, paste your code into the Guide Editor, right-click, click "Command Palette" from the menu that pops up, and then search for "Convert Indentation to Tabs."

  • Lines should not exceed 80 characters. If you need to, split comments across multiple lines to follow this rule.

  • Add comments throughout your code to explain your logic. Feel free to copy-paste the official USACO solution and improve it by adding more descriptive variable names and helpful comments.

  • Use universally understandable variable names, especially for Bronze and Silver. Should be more descriptive than what you would normally use in-contest.

  • Be consistent about formatting your code, unlike the following snippet. We don't care about which one you use (a+b or a + b), but pick one and stick with it throughout your entire code!

    a,b = (0,1)
    print(a + b)



Optional reading:


How to automatically format C++ code with links to style guides


C++ style guide

  • Do not use variable names that could conflict with using namespace std. For example, don't name a std::set "set."

  • Do not use variable-length arrays as discussed here.

  • Do not include code that doesn't do anything. In particular,

    • Do not include cout.tie(0) as discussed here.
    • Do not include optimization pragmas unless you show that they improve performance.
  • For Bronze through Gold in particular, do not use additional macros (especially loop macros) beyond the ones listed below (see Github #806):

    Code Snippet: C++ Short Template (Click to expand)
    int main() {
  • The C/C++ extension for Visual Studio Code supports code formatting using clang-format (details here). To indent using tabs, include the following in your C_Cpp.clang_format_fallbackStyle setting.

    { UseTab: AlignWithSpaces, TabWidth: 4, IndentWidth: 4 }

    You don't have to use a formatter, but doing so will ensure consistency.



  • Regarding I/O, Scanner is significantly slower than BufferedReader and should be avoided. You may use your own I/O template, but collapse it as described above.
  • It is good practice to not use constant size arrays in Java.
  • Use polymorphism when possible.
    • For example, List<Integer> list = new ArrayList<>() instead of ArrayList<Integer> list = new ArrayList<>().



  • Use snake_case to name variables in your code.

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