This problem is frozen

Mathematically equivalent to P01 (equal circles in the unit square) under d = 2r/(1 − 2r); Specht's reference table lists both quantities as columns of the same table. The catalogue retains the circle-packing formulation (P01).

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P15 · Packing and covering · Classic · Hard

Spreading points in the unit square · n = 6

Place n points in the unit square to maximize the minimum Euclidean distance between any two points.

Instancen = 6

ObjectiveMaximize the smallest distance between two points

Record comparison

the smallest distance between two points · Higher is better

Record	Value / interval	Author / holder	Source
Proven optimum	√13/6	See source attribution	web.archive.org ↗
Site record	0.54810912	Zrchedcxen	Record details ↓

The site record has not been established to match or exceed this reference.

Formal definition

ContainerThe unit square [0, 1] × [0, 1], with lower-left corner (0, 0) and upper-right corner (1, 1)
SubmissionExactly n distinct points
ConstraintsEvery point lies inside the unit square or on its boundary
Scoreδ(P) is the minimum Euclidean distance over all point pairs (the verifier compares δ(P)² using exact arithmetic internally) $δ (P) = \min_{1 \leq i < j \leq n} ‖ p_{i} - p_{j} ‖$
ObjectiveMaximize the minimum pairwise distance δ(P)

Open full editor ↗

Layout shown: site record

1y0

123456

0x1

VERIFIED CONSTRUCTIONthe closest pair

Getting a feel for it

Duality with equal-circle packing in a square

Placing n points in the unit square with minimum pairwise distance d is equivalent to packing n non-overlapping circles of radius d/2 in a square of side 1 + d (or radius r = d / (2 + 2d) in the unit square). At optimality, point pairs at distance d and points on the four edges lock into a rigid contact graph.

Proven optima and open frontier

Through the exact conversion to equal-circle packing in a square (csq), proofs and constructions in the csq literature transfer directly. Elementary partition proofs are included here for n = 2, 4, 5, and 9, while the remaining sizes follow the csq benchmark table.

Source

LAYOUT & HISTORY

Record details

Inspect the layout, solver notes and record history.

Record holderZrchedcxen

Solution methodHuman

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Record holder's solver noteNo solver note yet (expand)＋

The record holder has not shared a solver note yet.

Record history (5 changes)

ZrchedcxenHuman
0.5481091204→0.5481091208
2026-08-24
xxxHuman
0.543223441→0.54810912
2026-08-24
xxxHuman
0.513427124→0.543223441
2026-08-24
ZrchedcxenHuman
0.5→0.513427124
2026-08-24
ZrchedcxenHuman
0.333333333→0.5
2026-08-24

ANSWER FORMAT

How to write your answer

The container is a square of side 1. Its lower-left corner is the origin (0, 0) and its upper-right corner is (1, 1). Coordinates and lengths share one unit and are written as plain decimals such as "0.5", to at most nine decimal places.

Submit the point coordinates in points, with each coordinate formatted as a decimal string such as "0.5".

The current leader's answer

{
  "points": [
    [
      "0.000000000",
      "0.000000000"
    ],
    [
      "0.227334211",
      "0.500000000"
    ],
    [
      "1.000000000",
      "0.000000000"
    ],
    [
      "0.000000000",
      "1.000000000"
    ],
    [
      "0.775447983",
      "0.500000000"
    ],
    [
      "1.000000000",
      "1.000000000"
    ]
  ]
}

Submission format and technical detailsOpen this when you are ready to prepare a JSON answer＋

Instance parameters

{
  "n": 6
}

The current leader's answer

{
  "points": [
    [
      "0.000000000",
      "0.000000000"
    ],
    [
      "0.227334211",
      "0.500000000"
    ],
    [
      "1.000000000",
      "0.000000000"
    ],
    [
      "0.000000000",
      "1.000000000"
    ],
    [
      "0.775447983",
      "0.500000000"
    ],
    [
      "1.000000000",
      "1.000000000"
    ]
  ]
}

Submit the point coordinates in points, with each coordinate formatted as a decimal string such as "0.5". · Verifier v1.0.0

DISCUSSION

Discussion

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冻结，但贡献值……NUE_13#310 replies31d ago