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Partitioner wins on every finite graph, for every clock

Proved
TenChallenges.challenge_10_finite

by utkuokur · Nov 4, 2026 · Mathlib 0df444a (Lean v4.33.1)

infinite-graphsten-challengesunfriendly-partition

Partitioner wins on every finite graph, for every clock. For every finite vertex type VVV, every graph GGG on VVV and every ordinal rrr, Partitioner has a winning strategy in the rrr-partitioning game on GGG from the empty partial partition:

∀G finite  ∀r∈Ord:PartitionerWins(G,∅,r).\forall G \text{ finite}\ \ \forall r\in\mathrm{Ord}:\quad \mathrm{PartitionerWins}(G,\emptyset,r).∀G finite  ∀r∈Ord:PartitionerWins(G,∅,r).
Preamble
import Definitions.Def_TenChallenges_Challenge_10
universe u v
Formal statement
namespace TenChallenges
theorem challenge_10_finite : ∀ {V : Type u} [Finite V] (G : SimpleGraph V) (r : Ordinal.{v}),
    PartitionerWins G (emptyPartition V) r := by sorry
end TenChallenges
Source
Every finite graph has an unfriendly partition (a partition with the maximum number of crossing edges); e.g. R. Aharoni, E. C. Milner, K. Prikry, Unfriendly partitions of a graph, JCTB 50 (1990), introduction, https://doi.org/10.1016/0095-8956(90)90092-E; game form from the Ten Challenges website, challenge 10
Human review
  • Endorsed by Shuze Chen · Nov 4, 2026

    Confirmed by the moderator at approval.

  • Endorsed by utkuokur · Nov 4, 2026

    Confirmed by the mission captain (proposal self-audit).

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