MOJ: Free Training Manual (student)

Translation note. This manual is a translation of the Portuguese original. The command-line tools (moj, moj-contest, moj-comp) print their messages in Portuguese, and the command examples below are identical to the original.

Prefer the terminal? The moj-comp CLI also works in the training. You can search for a problem, download the statement, submit, and get the verdict without leaving the shell. Guide: /treino/cli.html.

Welcome to the MOJ Free Training. MOJ is an online judge. This manual shows, step by step, how to create your account, log in, find problems, submit your solution, and follow the result. It is for beginners, so it goes slowly and one step at a time.

Free Training is the place where you practice at your own pace. You choose the problem, write the code, submit it, and see the verdict. There is no deadline and no contest scoreboard. To compete for real, see MANUAL-CONTEST.md at the end of this document.

Contents

1. The home page
2. Create an account through Telegram
3. Log in
4. Forgot your password
5. Find problems
6. Solve a problem
7. Profile
8. My statistics
9. Editors page
10. More information

1. The home page

Open the MOJ address /. You do not need to log in to see the home page.

At the top is the menu bar, with these items:

Next to the menu is the language selector PT · EN · ES. The full site is available in the three languages. On the right is the login area. Before you log in, it shows the user and password fields. After you log in, it shows your avatar. The avatar opens a menu with shortcuts (My statistics, Profile, Log out…).

Lower on the page, you find:

• The highlight at the top, with the featured news item and the shortcut buttons Free Training →, Problem Management → and 📖 Help.
• The 🗂️ Problem Management card (it shows only for users who can create problems). It is for users who create problems (teachers, teaching assistants, authors). If you only want to train, you can ignore it.
• The 🏋️ Free Training card, with the Search problems → button.
• The 🏆 Top 10 of the users who solve the most. Click a name to open the public profile of that person (section 8).
• The 🔥 Most solved · last week and the ⌨ Editors · last week.
• The ✅ Recently solved list. It also links to the profiles of the users who solved.
• The list of contests, split into Open now, Upcoming and Ended, with a filter by name.
• The 📰 News.

To start to practice, click Free Training. It takes you to the address /treino/ (section 5).

2. Create an account through Telegram

The Free Training sign-up is at /treino/cadastro/, and Telegram confirms it. This prevents duplicate accounts. Thus, to sign up, you need a Telegram account.

Do these steps:

1. Fill in the form:
   • Full name (required).
   • Desired login (optional). It can have 2 to 32 characters: letters, numbers, and the symbols ., _ and -. If you leave it empty, the system uses your Telegram @ as the login.
   • University (optional).
2. Click Continue on Telegram →.
3. Open the mojinho bot on Telegram and tap Start. The sign-up page waits and confirms automatically when you talk to the bot.

An important point about the password:

Your password comes only in a private message on Telegram. It never shows on the web. Keep this message in a safe place.

When the sign-up is complete, go to the login screen (next section).

Under 18 (no Telegram)? A responsible teacher/admin creates the account and gives you the login and the password. These accounts always have a private profile until the age of 18. Details are in CONTAS-GERIDAS.md.

3. Log in

The login is at the top of every Free Training page. You see:

• a User field;
• a Password field;
• the Log in button.

Type the user and the password (the password is the one that the bot sent on Telegram). Then click Log in.

When you are logged in, the right corner of the bar shows your avatar. Click it to open a menu with shortcuts:

• My statistics
• Profile
• Log out
• and more options, if your account has extra permissions.

4. Forgot your password

There is no "forgot password" form on the web. You recover the password through Telegram.

If you linked Telegram to your account (this occurs at sign-up), do these steps:

1. Open the chat with the mojinho bot on Telegram.
2. Send the command /trocarsenha.
3. You get a new password in a private message on Telegram.

Then go back to the login screen and log in with the new password.

If your account has no Telegram (an account that a responsible person created; see the note in section 2), the responsible person who created the account resets the password.

5. Find problems

The problem search is at /treino/. You do not need to log in to see the list and read the statements. You must log in to see your personal progress and to submit a solution.

The page has two modes: the hub (the entry page) and the advanced search (the full list with filters). Any search or filter takes you from the hub to the advanced search automatically.

The hub

• Central search: type 2 or more letters. Grouped suggestions show in Collections, Tags and Problems (each problem shows its status ✓/…). Use the arrow keys ↑↓ and Enter, or click. If you press Enter without a selection, the advanced search opens with the typed text.
• Shortcuts: 🎲 random problem (it prefers a problem that you did not solve yet), 🌱 easy starters, 🚀 not solved yet and 🔬 advanced search.
• For you (shows when you are logged in): ▶ Pick up where you left off (your last attempt that has no AC yet) and 🎯 Suggested for you (a next problem).
• 📚 Featured collections: a carousel of cards. Each card shows the size of the collection and the bar of your progress. Click a card to filter the list by that collection. Scroll with the arrows ‹ › (or with your finger, on a phone). The link all (N) → opens the advanced search.
• 🔥 Most submitted this week: the 10 problems with the most submissions in the last 7 days.

The advanced search

The full list is always visible, with the filter rail on the left:

• Filter by title: type part of the name.
• My status (only when logged in): All / To solve / ✓ Solved / … Attempted.
• Difficulty: from very easy to hard. It uses the per-user rate of each problem (do the users who try succeed? solved ÷ attempted). The ranges are: ≥90% very easy, ≥70% easy, ≥50% medium, <50% hard. "new" means no data yet. This is the same scale as the problem statistics page, the profile, and the contest problem draw. Each option shows how many problems remain with it.
• Collections: the tree with checkboxes. You can select several at the same time (the list shows the union). Select a group (for example, obi) to get all its collections at once. The number on the right is your progress (for example, 20/140).
• Tags: select as many as you want. The problem must have all the selected tags. The counts update live as you filter.

Above the table are the chips of the active filters (the × removes them one at a time), the result count, and the sort order: Most solved, A–Z, Difficulty and Newest (the most recently published first).

The list comes in pages of 50. Tip: the URL keeps your filters. Copy the link to share a search. On a phone, the rail becomes the Filters (n) button.

To open a problem, click its title.

6. Solve a problem

When you click the title, you go to the address /treino/problema/?id=<id>. <id> is the code of the problem. The screen has two parts:

• On the left: the problem statement.
• On the right: the Submit solution panel.

At the top of the statement you find:

• the author(s) of the problem;
• the collections that the problem is in;
• the tags (they start blurred, with a show/hide tags link);
• the time limit per language;
• a statistics button for the problem;
• the ⬇ Samples button. It downloads the input and the output of each sample as files, in a zip.

Each sample block in the statement has a Copy button in its title. One click copies the full block, with the final line break.

When the problem has the statement in more than one language, the chips PT · EN · ES show above the text. Click a chip to change the language. The title changes too. MOJ remembers your selection for the next problems. In the problem list, the EN ES badge next to the title shows which problems have a translation.

How to submit your solution

You must be logged in to submit. In the Submit solution panel:

1. Select the language in the menu. Each option shows the time limit of that language.
2. Write your code in one of these two ways:
   • Type it in the editor. The editor (its name is CodeMirror) comes with a template of the selected language to help you start.
   • Or upload a file in the or file: field. When you select a file, MOJ sends the file.
3. Click Submit solution.

What you see after the click. There is no pop-up window. The button shows a spinner with Sending… while the submission goes to the server, and it does not accept another click. Then it becomes green for a moment, with ✓ Sent. Below it, the confirmation ✓ Submitted at 14:03:12 — C++ shows, and the submission appears in the history immediately. After the submission, the file field is empty.

MOJ does not send an empty editor or the language template without changes: it asks you to write your solution.

Same code again. If the code is equal to the last code that you submitted for that problem, in the same language, the first click does not submit. The button becomes orange and shows Same code as the 14:03 submission — submit again?. Click again within 5 seconds to submit it anyway. A different language counts as new code.

At most 3 submissions in the queue. Your account can have up to 3 submissions waiting for a verdict at the same time. The 4th one is refused with the message "You already have 3 submissions waiting for a verdict". Wait for a result and submit again. The limit also applies to virtual participation. It makes sure that no account takes the judge for itself.

The editor has some conveniences:

• Full screen: the editor fills the full window.
• New window: opens a mode with only the editor.
• ▾ Hide editor / ▸ Show editor: makes the editor small when you do not need it.

Follow the result

Below is the Submission history, with these columns:

The buttons in the Actions column are:

• ✎ (editor): loads that code into the editor again.
• code: downloads the source file that you submitted.
• log: opens the judgment report.

While the result is pending, a loading indicator shows, and the page updates automatically when the verdict is ready. You do not need to reload the page manually.

Below the verdict is a summary line, for example:

Passed 3/5 tests

The details of each language and of how data input and output work are on the site's Help page (/treino/ajuda/). This page also has the starter code for each language. The link "📖 How to submit" shows next to the language selector when you submit.

7. Profile

Your profile is at /treino/perfil/. It has sections, and each section has its own save button. Change what you want and save one section at a time.

⚠ Be careful when you change the Username:

A change of handle updates all your history to the new name. There is a limit of changes per year (the default is 2). The screen shows how many you already used.

This page is where you edit the profile. What other users see, your public profile, is at /treino/stat/?user=<your login>. The next section is about it.

8. My statistics

Each user has a public profile at /treino/stat/?user=<login>. To open yours, use the avatar menu → 📊 My statistics. To open the profile of another user, click the name (for example, in the Top 10 on the home page).

From top to bottom, the profile shows:

• Header: photo (or initials), university, member since, favorite editor (with its position in the editor ranking) and the last submission.
• Cards: problems solved, submissions, acceptance rate, AC on first try, attempts to solve, streaks (consecutive days with a submission) and the favorite language.
• Charts: solved problems over time, activity map (26 weeks), rhythm day × hour, verdicts, performance per language, difficulty of solved, progress by collection, strengths by tag, and the Open list (problems that you attempted and did not solve yet — a very good queue to return to training).
• 🏅 Achievements: automatic medals — First AC, Centurion (100 solved), streaks, Polyglot, collection complete, and others. The locked medals show in gray, with how much is missing (for example, 82/100). The full catalog and the rules are in PERFIL.md.
• Paginated history (25 per page), with filters by problem, verdict and language, and sort by column. The code/log links show only for the owner.

Remember: if your profile is private (section 7), all of this shows only for you. Your name is also removed from the public lists on the home page.

9. Editors page

The page /treino/editores/ collects the statistics of the favorite editors that users declare: a ranking and the distribution of who uses what.

Tip: do you want to show in this ranking? Declare your editor in the Details section of the Profile (see section 7).

9½. Virtual participation: do an ended contest again

Some ended contests have the 🕹️ Virtual button on their card (home page and contests archive). It opens the virtual participation. You do the full contest again, with a clock, against the official scoreboard. The official teams solve the problems at the same minute as in the real contest.

1. Read the rules and accept them. Do not participate if you already saw the problems. Do the full contest.
2. Select Start now or Schedule (up to 7 days ahead; you can cancel the schedule).
3. In the arena: open a problem, select the file, and submit. The verdict shows in My submissions. The scoreboard highlights your row, with the position that you would have.
4. Finish now ends before the time is over.

Scoreboard filters. The bar is the same as on the contest scoreboard: Board (for example, only the official teams, without guests), Flag, University, Site and the search. When a filter is active, the large number is the position in the filtered subset. The small number is the overall position. Your row always shows. My picks. Click the 📌 on a virtual row to pin that person. That person then always shows on the scoreboard, with any filter. The 📌 Picks button opens the list. In the list, you can search by name or login, select and clear entries, or add the login of a user who did not do the virtual participation of this contest yet. The list belongs to your account and applies to all contests. Example: pick your friends, select a Site, and see the position of each friend among the teams of that site.

The Virtuals selector selects one of these: all the virtual participants, only the picks, only you, or none. The Site filter does not hide the virtual participants. Thus you can compare your result with the teams of that site.

Give up without a record: the Give up button is available in the first 15 minutes, or while you have no accepted problem. When you give up, you get the attempt back, 2 times at most. After that, the start is final. If the time ends with no accepted problem, it counts as giving up.

After: your row stays on the virtual scoreboard of the contest, marked as virtual. Each account does the virtual participation of a contest one time. The submissions stay in your training history.

When you are not logged in, the same page shows the Replay. Drag the time control to see the scoreboard at any minute of the contest.

10. More information

• For the details of how to submit in each language and of how data input and output work, see the Help page (/treino/ajuda/).
• To compete in a contest (with a deadline and a scoreboard), see MANUAL-CONTEST.md.

Good training, and good code.