P87 · Packing and covering · Classic · Easy

Equal discs covering a disc · n = 36

Cover the largest possible disc with n unit-radius discs. Maximise the covered disc radius.

Instancen = 36
ObjectiveMaximize covered disc radius

Record comparison

covered disc radius · Higher is better
RecordValue / intervalAuthor / holderSource
External best known——No reference listed
Site recordNo player record yet——

Formal definition

  • ContainerThe editor and certificate normalize to the closed unit disc centred at (1,1). This is a coordinate convention only; scores use the literature's unit-piece scale. Boundary contact is allowed.
  • SubmissionSubmit {radius, placements:[{x,y,turn},…]}, with decimal strings of at most nine places. x,y are centres; circles require turn=0, polygons use turn=tan(θ/2). Coordinates and turn lie in ±4; 0 < radius ≤ 4.
  • ConstraintsThe n distinct centres lie in the target disc. Covering discs may overlap and protrude, but must cover every target point.
  • PrecisionInput decimals are exact rationals; regular-polygon vertices are algebraic, not rounded templates. Feasibility has no floating-point tolerance. A finite-decimal certificate is not a continuous optimality proof.
  • ObjectiveCovered disc radius R = 1/r, larger is better.
Open the full editor ↗

Layout shown: starter layout

VERIFIED CONSTRUCTIONVERIFIED CONSTRUCTION

Getting a feel for it

Source and certificate

External targets are converted with their printed precision; decimal coordinate certificates are separate. Reconstruction loss never lowers the literature target, and a source construction is not automatically an optimality proof.

Source
The current arrangement for Equal discs covering a disc n = 36
LAYOUT & HISTORY

Starter layout

Inspect the layout, solver notes and record history.

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ANSWER FORMAT

How to write your answer

the closed unit disc centred at (1,1)

Submit {radius, placements:[{x,y,turn},…]}, with decimal strings of at most nine places. x,y are centres; circles require turn=0, polygons use turn=tan(θ/2). Coordinates and turn lie in ±4; 0 < radius ≤ 4.

Starter answer

{
  "placements": [
    {
      "turn": "0",
      "x": "1.058006904",
      "y": "1.053516398"
    },
    {
      "turn": "0",
      "x": "0.802104665",
      "y": "0.803855008"
    },
    {
      "turn": "0",
      "x": "1.097184416",
      "y": "0.699512111"
    },
    {
      "turn": "0",
      "x": "0.715477885",
      "y": "1.115646736"
    },
    {
      "turn": "0",
      "x": "1.348267670",
      "y": "0.940603472"
    },
    {
      "turn": "0",
      "x": "0.967085238",
      "y": "1.352423188"
    },
    {
      "turn": "0",
      "x": "1.319478380",
      "y": "1.296985858"
    },
    {
      "turn": "0",
      "x": "0.855950747",
      "y": "0.456341377"
    },
    {
      "turn": "0",
      "x": "0.459284042",
      "y": "0.866825329"
    },
    {
      "turn": "0",
      "x": "1.414486256",
      "y": "0.597235905"
    },
    {
      "turn": "0",
      "x": "0.620747337",
      "y": "1.431048800"
    },
    {
      "turn": "0",
      "x": "1.600373313",
      "y": "1.206376153"
    },
    {
      "turn": "0",
      "x": "1.231569457",
      "y": "1.584879969"
    },
    {
      "turn": "0",
      "x": "0.548568139",
      "y": "0.555547354"
    },
    {
      "turn": "0",
      "x": "1.174730492",
      "y": "0.354241706"
    },
    {
      "turn": "0",
      "x": "0.385130071",
      "y": "1.192557902"
    },
    {
      "turn": "0",
      "x": "1.644243383",
      "y": "0.858380549"
    },
    {
      "turn": "0",
      "x": "0.876161968",
      "y": "1.650814786"
    },
    {
      "turn": "0",
      "x": "1.580329837",
      "y": "1.559841581"
    },
    {
      "turn": "0",
      "x": "0.607787872",
      "y": "0.206235278"
    },
    {
      "turn": "0",
      "x": "0.898078461",
      "y": "0.123740189"
    },
    {
      "turn": "0",
      "x": "0.194825776",
      "y": "0.674407079"
    },
    {
      "turn": "0",
      "x": "1.522993949",
      "y": "0.281595209"
    },
    {
      "turn": "0",
      "x": "0.127684941",
      "y": "0.947548065"
    },
    {
      "turn": "0",
      "x": "1.719340048",
      "y": "0.504734312"
    },
    {
      "turn": "0",
      "x": "0.310835985",
      "y": "1.547267280"
    },
    {
      "turn": "0",
      "x": "1.889930175",
      "y": "1.125163317"
    },
    {
      "turn": "0",
      "x": "0.530788090",
      "y": "1.751061988"
    },
    {
      "turn": "0",
      "x": "1.839383809",
      "y": "1.480066376"
    },
    {
      "turn": "0",
      "x": "1.164130869",
      "y": "1.872024447"
    },
    {
      "turn": "0",
      "x": "1.513999205",
      "y": "1.822645260"
    },
    {
      "turn": "0",
      "x": "0.299653711",
      "y": "0.358328897"
    },
    {
      "turn": "0",
      "x": "1.246652587",
      "y": "0.052386222"
    },
    {
      "turn": "0",
      "x": "0.081304699",
      "y": "1.287506926"
    },
    {
      "turn": "0",
      "x": "1.935820141",
      "y": "0.771115749"
    },
    {
      "turn": "0",
      "x": "0.820180653",
      "y": "1.952321535"
    }
  ],
  "radius": "0.198654505"
}
Submission format and technical detailsOpen this when you are ready to prepare a JSON answer+

Instance parameters

{
  "n": 36,
  "sides": 5
}

Starter answer

{
  "placements": [
    {
      "turn": "0",
      "x": "1.058006904",
      "y": "1.053516398"
    },
    {
      "turn": "0",
      "x": "0.802104665",
      "y": "0.803855008"
    },
    {
      "turn": "0",
      "x": "1.097184416",
      "y": "0.699512111"
    },
    {
      "turn": "0",
      "x": "0.715477885",
      "y": "1.115646736"
    },
    {
      "turn": "0",
      "x": "1.348267670",
      "y": "0.940603472"
    },
    {
      "turn": "0",
      "x": "0.967085238",
      "y": "1.352423188"
    },
    {
      "turn": "0",
      "x": "1.319478380",
      "y": "1.296985858"
    },
    {
      "turn": "0",
      "x": "0.855950747",
      "y": "0.456341377"
    },
    {
      "turn": "0",
      "x": "0.459284042",
      "y": "0.866825329"
    },
    {
      "turn": "0",
      "x": "1.414486256",
      "y": "0.597235905"
    },
    {
      "turn": "0",
      "x": "0.620747337",
      "y": "1.431048800"
    },
    {
      "turn": "0",
      "x": "1.600373313",
      "y": "1.206376153"
    },
    {
      "turn": "0",
      "x": "1.231569457",
      "y": "1.584879969"
    },
    {
      "turn": "0",
      "x": "0.548568139",
      "y": "0.555547354"
    },
    {
      "turn": "0",
      "x": "1.174730492",
      "y": "0.354241706"
    },
    {
      "turn": "0",
      "x": "0.385130071",
      "y": "1.192557902"
    },
    {
      "turn": "0",
      "x": "1.644243383",
      "y": "0.858380549"
    },
    {
      "turn": "0",
      "x": "0.876161968",
      "y": "1.650814786"
    },
    {
      "turn": "0",
      "x": "1.580329837",
      "y": "1.559841581"
    },
    {
      "turn": "0",
      "x": "0.607787872",
      "y": "0.206235278"
    },
    {
      "turn": "0",
      "x": "0.898078461",
      "y": "0.123740189"
    },
    {
      "turn": "0",
      "x": "0.194825776",
      "y": "0.674407079"
    },
    {
      "turn": "0",
      "x": "1.522993949",
      "y": "0.281595209"
    },
    {
      "turn": "0",
      "x": "0.127684941",
      "y": "0.947548065"
    },
    {
      "turn": "0",
      "x": "1.719340048",
      "y": "0.504734312"
    },
    {
      "turn": "0",
      "x": "0.310835985",
      "y": "1.547267280"
    },
    {
      "turn": "0",
      "x": "1.889930175",
      "y": "1.125163317"
    },
    {
      "turn": "0",
      "x": "0.530788090",
      "y": "1.751061988"
    },
    {
      "turn": "0",
      "x": "1.839383809",
      "y": "1.480066376"
    },
    {
      "turn": "0",
      "x": "1.164130869",
      "y": "1.872024447"
    },
    {
      "turn": "0",
      "x": "1.513999205",
      "y": "1.822645260"
    },
    {
      "turn": "0",
      "x": "0.299653711",
      "y": "0.358328897"
    },
    {
      "turn": "0",
      "x": "1.246652587",
      "y": "0.052386222"
    },
    {
      "turn": "0",
      "x": "0.081304699",
      "y": "1.287506926"
    },
    {
      "turn": "0",
      "x": "1.935820141",
      "y": "0.771115749"
    },
    {
      "turn": "0",
      "x": "0.820180653",
      "y": "1.952321535"
    }
  ],
  "radius": "0.198654505"
}

Submit {radius, placements:[{x,y,turn},…]}, with decimal strings of at most nine places. x,y are centres; circles require turn=0, polygons use turn=tan(θ/2). Coordinates and turn lie in ±4; 0 < radius ≤ 4. · Verifier v1.0.0

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