open.kattis.com

Yes. Kattis is suitable for beginners, and the site itself says so: the problem archive welcomes new users and tells them to "just register and start solving." The main catch is that Kattis is a bare problem archive rather than a guided course — it gives you thousands of problems and a difficulty scale, but no lessons or explanations. If you already know the basics of one programming language and want practice, you can start immediately. If you have never written code, you will need a separate learning resource first.

What Kattis Actually Is

Kattis (open.kattis.com) is a programming problem archive. You read a problem statement, write a program that reads input and produces the required output, and submit it. The judge runs your code against test cases and tells you whether it passes.

The homepage describes it plainly: "Here you can find thousands of programming problems to solve. If you're new here you're very much welcome! Just register and start solving."

That is the whole onboarding. There is no tutorial track, no video course, and no explanation of algorithms — just problems, a difficulty rating, and a scoreboard.

Why It Works for Beginners

The difficulty system is the main reason a newcomer can use Kattis without getting lost. Each problem carries a point value that reflects how hard it is, and the homepage groups suggested problems into tiers:

A beginner should stay in the Trivial and Easy rows until solving them feels routine. The jump from Easy to Medium is real — the Medium and Hard examples above involve bitmasking, elliptic curve arithmetic, and flow problems, which assume you already know specific algorithms.

The "Suggested problems" list on the homepage is the fastest way to find a starting point, because it mixes tiers instead of forcing you to browse the full archive blind.

How to Start, Step by Step

1. Register an account. The site's own instruction is to register and begin. You need an account for your submissions to be tracked and scored.
2. Pick a language you already know. Kattis accepts many common languages; the problem is judged on output, not on which language you chose. Use whatever you can already write a loop and read input in.
3. Solve one Trivial problem first. Take Cetvrta (1.3 pt) or Sum Squared Digits Function (1.4 pt). The goal of the first problem is not the algorithm — it is learning the input/output format, which is where most first submissions fail.
4. Read the input/output specification twice. Kattis problems state exactly what input looks like and exactly what output must be printed. Extra spaces, missing newlines, or debug text will cause a wrong answer.
5. Submit and read the verdict. If you get "Wrong Answer," compare your output character by character against the spec. If you get a runtime error, check for array bounds and input parsing.
6. Move up one tier at a time. Once Trivial feels easy, work through Easy problems. Only then attempt Medium.

What Beginners Should Expect to Struggle With

• No explanations. When you are stuck, Kattis will not tell you why. You need to debug on your own or look elsewhere.
• Strict output matching. The judge compares your output to the expected output exactly. A trailing space or a missing final newline is enough to fail.
• Difficulty is relative. A 1.3-point problem is trivial only if you are comfortable with basic input parsing and arithmetic in your language.
• Scoring is cumulative. The ranklist on the homepage shows top users with scores in the thousands (the top entry is 18448.0), which reflects years of solving. Do not read the leaderboard as a beginner benchmark.

When Kattis Is the Wrong Choice

Skip Kattis for now if any of these apply:

• You have not yet written a program that reads input and prints output.
• You want structured lessons with explanations of algorithms.
• You want a course with a defined curriculum and deadlines.

In those cases, learn the language basics elsewhere first, then come back — Kattis will still be there, and the Trivial tier will still be waiting.

Kattis is an online programming problem archive where you can find thousands of programming problems to solve. If you're new, you register an account and start solving; the site tracks your score and places you on a ranklist. It's aimed at anyone who wants to practice competitive programming or algorithmic problem-solving, from beginners working through trivial problems to experienced solvers tackling hard ones.

What you can do on the site

The homepage presents the archive as its core feature: "Here you can find thousands of programming problems to solve." Beyond browsing and submitting solutions, the site surfaces several community views:

• Suggested problems — a curated list spanning difficulty levels, so you don't have to guess where to start.
• Ranklist — individual users ranked by score.
• Affiliations — organizations (mostly universities) ranked by combined score.
• Countries — countries ranked by combined score.

How difficulty and scoring work

Problems carry a point value that reflects difficulty. The suggested problems on the homepage show this spread clearly:

So a problem's point value is a rough proxy for how hard it is — higher points generally mean harder problems. Your total score accumulates across solved problems and determines your rank.

Who appears on the leaderboards

The ranklist shows individual solvers with their scores. At the time of the source data, the top entries were:

1. Nick Wu — 18448.0
2. Atli Fannar Franklín — 18313.0
3. Doug Goodman — 15863.8
4. Jeremy Lim — 14639.5
5. Andreas Björklund — 12622.6

The affiliation ranking aggregates scores by institution:

And the country ranking aggregates by nation:

These three views let you compare yourself against individuals, schools, or countries depending on what motivates you.

How to get started

1. Register an account — the site states that if you're new, you "just register and start solving."
2. Pick a problem — use the suggested problems list to find one matching your level, or browse the archive.
3. Solve and submit — your score updates as you solve problems, feeding into the ranklist.

The suggested problems list is the most direct entry point because it already sorts problems by difficulty, so you can start with a trivial 1.3-point problem and work upward rather than searching the full archive blind.

When Kattis is a good fit

Kattis suits you if you want a large, ranked problem archive with clear difficulty signals and social comparison through individual, school, and country leaderboards. It's less about structured courses and more about self-directed practice against a scored problem set. If you're preparing for competitive programming, working through algorithm topics, or representing a university, the affiliation and country rankings give the practice an extra dimension beyond your own score.

Kattis ranks users by total score: the more points you accumulate from solved problems, the higher you appear on the ranklist. The site publishes three separate leaderboards — individual users, affiliations (usually universities), and countries — so the same solving activity feeds into several competitive views at once. The exact point value of any single problem is set by Kattis and shown on the problem itself; the homepage only displays a difficulty label and a point figure for each suggested problem.

The three ranklists

The Kattis Problem Archive homepage shows a "Ranklist" section alongside "Affiliations" and "Countries." Each is a top-8 snapshot rather than the full standings.

The user list is ordered purely by score, descending. The affiliation and country lists use the same ordering logic but aggregate across everyone associated with that institution or country.

How scoring works

Each problem carries a point value. On the homepage's "Suggested problems" table, values run from 1.3 pt (Cetvrta, labeled Trivial) up to 7.8 pt (Pipe Stream, labeled Hard):

• Trivial — Cetvrta, 1.3 pt
• Trivial — Sum Squared Digits Function, 1.4 pt
• Easy — Lawn Mower, 1.7 pt
• Easy — Robot Protection, 2.2 pt
• Medium — Bitmask, 3.2 pt
• Medium — Elliptic Curve Point Multiplication, 3.7 pt
• Hard — Flow Finder, 7.7 pt
• Hard — Pipe Stream, 7.8 pt

Two things follow from this table. First, difficulty labels and point values rise together in the sample shown, so harder problems are worth more. Second, the spread is wide — a hard problem is worth roughly six times a trivial one — which means a ranklist position reflects both how many problems you solve and how hard they are.

Your total score is the sum of the points from the problems you have solved. To move up, you either solve more problems or solve higher-value ones.

Reading a ranklist position

A score alone doesn't tell you how a user got there. Two users near each other on the list may have very different profiles — one grinding through many easy problems, another clearing a smaller number of hard ones. The homepage doesn't break scores down by difficulty, so the ranklist shows the total only.

The same applies to the affiliation and country tables. A country's score aggregates its users, so a country with many active solvers can outrank one with a few strong ones. The homepage shows the aggregate, not the number of contributors.

Practical implications

• If you want a higher personal rank, prioritize problems with larger point values once you can handle them; a single 7.7 pt solve is worth several trivial ones.
• If you're tracking an institution or country, remember the score is a sum across all associated users, so recruiting more solvers raises the total even if individual skill doesn't change.
• If you're new, the "Suggested problems" table is a reasonable entry point: start at the Trivial and Easy rows, then work upward as the point values climb.

The homepage presents only the top 8 in each category. For anything beyond that, you'd need the full ranklist pages, which the homepage excerpt doesn't cover.

Kattis groups problems into four named difficulty bands — Trivial, Easy, Medium, and Hard — and assigns each problem a numeric point value that increases with difficulty. On the problem archive homepage, the "Suggested problems" section lists one example problem per band alongside its score, so you can gauge the jump between levels before you start solving. If you are new, the practical approach is to start at the Trivial or Easy end and move up as your accepted-solution count grows.

The four difficulty bands and their point ranges

The homepage's suggested-problems list shows the following examples, which illustrate how the bands map to scores:

Two things stand out from this table. First, the bands overlap in score: a 2.2-point problem is still labeled Easy, while a 3.2-point problem is already Medium. The label is the primary signal; the score is a finer-grained tiebreaker within and across bands. Second, the gap between Medium and Hard is much larger than the gap between Trivial and Easy — the suggested Hard problems sit at roughly double the suggested Medium scores.

How to use the labels to pick a problem

The difficulty label answers "roughly how much experience do I need," and the point value answers "how much is this worth relative to its neighbors." A workable selection routine:

1. Match the band to your current level. If you are new to competitive programming, stay in Trivial and Easy until you can solve them reliably.
2. Use the score to fine-tune within a band. Inside Easy, a 1.4-point problem is a gentler start than a 2.2-point one.
3. Treat a band jump as a real jump. Moving from Easy to Medium, or Medium to Hard, is not a small step — the suggested problems show the score roughly doubling at the Medium-to-Hard boundary.

The "Suggested problems" list itself is the intended entry point: it exists so that a first-time visitor does not have to browse thousands of problems to find a starting point.

What the score is not

The point value is a difficulty indicator, not a measure of time or effort in any fixed unit. Two problems with the same score can require very different techniques. The homepage also shows a global ranklist where top users have accumulated scores in the tens of thousands (the top entry is 18,448.0), which tells you the scale is cumulative across many solved problems rather than a per-problem rating. Affiliation and country leaderboards use the same cumulative scoring, so a high rank reflects volume and difficulty of problems solved together, not a single hard problem.

Practical starting point

Register on the site, open the problem archive, and begin with the Trivial and Easy entries in the suggested list. As you clear them, step up one band at a time. The label tells you whether you belong in that band; the score tells you where inside it to start.