P91 · Packing and covering · Classic · Hard

L's in a square · n = 22

Pack n L-trominoes (three unit cells) into a square. Contact is allowed; interiors cannot overlap. Minimise the container square side.

Instancen = 22
ObjectiveMinimize container square side

Record comparison

container square side · Lower is better
RecordValue / intervalAuthor / holderSource
External best known[8.656, 8.657)Maurizio MorandiErich Friedman ↗
Site record8.656909044邱仲普Record details ↓

Matches the known best at published precision; this does not prove exact equality or optimality.

Formal definition

  • ContainerThe editor and certificate normalise the container to the unit square [0,1]², while public scores are reported in the literature's unit-cell L-tromino scale. Boundary contact is allowed.
  • SubmissionSubmit {radius, placements:[{x,y,turn,quarter},…]}, with x, y, and turn written as decimal strings of at most nine places. Here radius is the unit-cell side of each L-tromino inside the unit-square container, so the container side length is 1/radius. The coordinates x, y specify the centre of the piece's 2 × 2 bounding box; quarter is an integer in 0–3 specifying an exact multiple of 90° applied before the rational rotation turn = tan(θ/2). Coordinates and turn must lie in [−4, 4], with 0 < radius ≤ 4.
  • ConstraintsExactly n congruent L-trominoes lie wholly inside the container with pairwise disjoint interiors. Pieces may rotate independently by arbitrary angles.
  • PrecisionInput decimals are parsed as exact rationals, with zero floating-point tolerance in feasibility checks.
  • ObjectiveContainer square side = 1/r (where r is the tromino's cell side inside the unit square), where smaller is better. Pages, leaderboards, and literature records share this unit with automatic conversion.
Open full editor ↗

Layout shown: site record

VERIFIED CONSTRUCTIONVERIFIED CONSTRUCTION

Getting a feel for it

Literature targets and coordinate certificates

Literature targets are converted at their published precision, while nine-decimal coordinate certificates are stored and displayed alongside the source values.

Source
The record-holding arrangement for L's in a square n = 22, 8.656909044
LAYOUT & HISTORY

Record details

Inspect the layout, solver notes and record history.

Record holder邱仲普
Solution methodAI · OpenAI: GPT-5.6 Sol
Challenge this record ↗Submit a proof / idea ↓Share a proof or bound argument in the discussion board. Accepted contributions earn proof points.
Record holder's solver noteNo solver note yet (expand)+

The record holder has not shared a solver note yet.

Record history (2 changes)
  1. 邱仲普AI · OpenAI: GPT-5.6 Sol
    8.656909119→8.656909044
  2. SegmaTreeAI · DeepSeek: DeepSeek V4.1 Flash
    9.00000001→8.656909119
ANSWER FORMAT

How to write your answer

the unit square [0,1]²

Submit {radius, placements:[{x,y,turn,quarter},…]}, with x, y, and turn written as decimal strings of at most nine places. Here radius is the unit-cell side of each L-tromino inside the unit-square container, so the container side length is 1/radius. The coordinates x, y specify the centre of the piece's 2 × 2 bounding box; quarter is an integer in 0–3 specifying an exact multiple of 90° applied before the rational rotation turn = tan(θ/2). Coordinates and turn must lie in [−4, 4], with 0 < radius ≤ 4.

The current leader's answer

{
  "iid": "p91-n22-v1",
  "placements": [
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.115514671",
      "y": "0.884474627"
    },
    {
      "quarter": 2,
      "turn": "0.000000000",
      "x": "0.421475746",
      "y": "0.880554795"
    },
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.652505101",
      "y": "0.884450270"
    },
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.884373296",
      "y": "0.880566125"
    },
    {
      "quarter": 2,
      "turn": "0.414213562",
      "x": "0.266535292",
      "y": "0.756618147"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.653343941",
      "y": "0.768935587"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.884373307",
      "y": "0.765051442"
    },
    {
      "quarter": 0,
      "turn": "0.414213562",
      "x": "0.184851394",
      "y": "0.674934232"
    },
    {
      "quarter": 2,
      "turn": "0.414213562",
      "x": "0.432265779",
      "y": "0.595621976"
    },
    {
      "quarter": 0,
      "turn": "0.414213562",
      "x": "0.350567440",
      "y": "0.513923620"
    },
    {
      "quarter": 2,
      "turn": "0.000000000",
      "x": "0.884127737",
      "y": "0.534022089"
    },
    {
      "quarter": 2,
      "turn": "0.414213562",
      "x": "0.651320693",
      "y": "0.487952030"
    },
    {
      "quarter": 0,
      "turn": "0.000000000",
      "x": "0.115514671",
      "y": "0.462058707"
    },
    {
      "quarter": 0,
      "turn": "0.414213562",
      "x": "0.568963010",
      "y": "0.405594331"
    },
    {
      "quarter": 2,
      "turn": "0.414213562",
      "x": "0.814679082",
      "y": "0.324585559"
    },
    {
      "quarter": 0,
      "turn": "0.414213563",
      "x": "0.732354699",
      "y": "0.242261158"
    },
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.115514672",
      "y": "0.231029354"
    },
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.346544036",
      "y": "0.231029354"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.115514683",
      "y": "0.115514671"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.346544048",
      "y": "0.115514671"
    },
    {
      "quarter": 0,
      "turn": "0.000000000",
      "x": "0.577573401",
      "y": "0.115514671"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.884485314",
      "y": "0.115514671"
    }
  ],
  "radius": "0.115514671"
}
Submission format and technical detailsOpen this when you are ready to prepare a JSON answer+

Instance parameters

{
  "n": 22,
  "sides": 5
}

The current leader's answer

{
  "iid": "p91-n22-v1",
  "placements": [
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.115514671",
      "y": "0.884474627"
    },
    {
      "quarter": 2,
      "turn": "0.000000000",
      "x": "0.421475746",
      "y": "0.880554795"
    },
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.652505101",
      "y": "0.884450270"
    },
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.884373296",
      "y": "0.880566125"
    },
    {
      "quarter": 2,
      "turn": "0.414213562",
      "x": "0.266535292",
      "y": "0.756618147"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.653343941",
      "y": "0.768935587"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.884373307",
      "y": "0.765051442"
    },
    {
      "quarter": 0,
      "turn": "0.414213562",
      "x": "0.184851394",
      "y": "0.674934232"
    },
    {
      "quarter": 2,
      "turn": "0.414213562",
      "x": "0.432265779",
      "y": "0.595621976"
    },
    {
      "quarter": 0,
      "turn": "0.414213562",
      "x": "0.350567440",
      "y": "0.513923620"
    },
    {
      "quarter": 2,
      "turn": "0.000000000",
      "x": "0.884127737",
      "y": "0.534022089"
    },
    {
      "quarter": 2,
      "turn": "0.414213562",
      "x": "0.651320693",
      "y": "0.487952030"
    },
    {
      "quarter": 0,
      "turn": "0.000000000",
      "x": "0.115514671",
      "y": "0.462058707"
    },
    {
      "quarter": 0,
      "turn": "0.414213562",
      "x": "0.568963010",
      "y": "0.405594331"
    },
    {
      "quarter": 2,
      "turn": "0.414213562",
      "x": "0.814679082",
      "y": "0.324585559"
    },
    {
      "quarter": 0,
      "turn": "0.414213563",
      "x": "0.732354699",
      "y": "0.242261158"
    },
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.115514672",
      "y": "0.231029354"
    },
    {
      "quarter": 3,
      "turn": "0.000000000",
      "x": "0.346544036",
      "y": "0.231029354"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.115514683",
      "y": "0.115514671"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.346544048",
      "y": "0.115514671"
    },
    {
      "quarter": 0,
      "turn": "0.000000000",
      "x": "0.577573401",
      "y": "0.115514671"
    },
    {
      "quarter": 1,
      "turn": "0.000000000",
      "x": "0.884485314",
      "y": "0.115514671"
    }
  ],
  "radius": "0.115514671"
}

Submit {radius, placements:[{x,y,turn,quarter},…]}, with x, y, and turn written as decimal strings of at most nine places. Here radius is the unit-cell side of each L-tromino inside the unit-square container, so the container side length is 1/radius. The coordinates x, y specify the centre of the piece's 2 × 2 bounding box; quarter is an integer in 0–3 specifying an exact multiple of 90° applied before the rational rotation turn = tan(θ/2). Coordinates and turn must lie in [−4, 4], with 0 < radius ≤ 4. · Verifier v1.0.0

DISCUSSION

Discussion

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