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Permutation

提出詳細

type Impl<T,U> =
  T extends unknown
  ? (Exclude<U,T> extends never ? [T] : [T,...Wrapper<Exclude<U,T>>])
  : never
type Wrapper<T> = {
  [key in T & PropertyKey]: Impl<key,T>
}[T & PropertyKey]
type Permutation<T> = [T] extends [never] ? [] : Wrapper<T>
提出日時2023-09-13 16:27:51
問題Permutation
ユーザーsankantsu
ステータスAccepted
テストケース
import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<Permutation<'A'>, ['A']>>,
  Expect<Equal<Permutation<'A' | 'B' | 'C'>, ['A', 'B', 'C'] | ['A', 'C', 'B'] | ['B', 'A', 'C'] | ['B', 'C', 'A'] | ['C', 'A', 'B'] | ['C', 'B', 'A']>>,
  Expect<Equal<Permutation<'B' | 'A' | 'C'>, ['A', 'B', 'C'] | ['A', 'C', 'B'] | ['B', 'A', 'C'] | ['B', 'C', 'A'] | ['C', 'A', 'B'] | ['C', 'B', 'A']>>,
  Expect<Equal<Permutation<never>, []>>,
]