05423-hard-intersection

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// string & unknown η­‰εŒδΊŽ string
type Intersection<T extends any[]> = T extends [infer R, ...infer rest] ? (R extends any[] ? R[number] : R) & Intersection<rest> : unknown

Solution by ouzexi #34307 

type Intersection<T extends any[]> = T extends [infer L, ...infer R]
  ? L extends any[]
    ? L[number] & Intersection<R>
    : L & Intersection<R>
  : unknown;


// θΏ™ι‡Œζœ€εŽδΈ€δΈͺεˆ†ζ”―εΊ”θ―₯是 unknownοΌŒε› δΈΊunknownε’Œδ»»δ½•η±»εž‹ε–δΊ€ε‰η±»εž‹ιƒ½η­‰δΊŽθ―₯η±»εž‹
type Result1 = 1 & unknown   // 1
type Result2 = any & unknown // any
type Result3 = {} & unknown // {}

Solution by Vampirelee #32646 

type Normalize<T> = T extends any[] ? T[number] : T
type Intersection<T extends any[]> = T extends [infer Head, ...infer Tail] 
                                      ? Tail['length'] extends 0
                                        ? Normalize<Head>
                                        : Normalize<Head> & Intersection<Tail>
                                      : never

Solution by mrf1freak #26948 

type Intersection<T> = T extends [infer F, ...infer R]
  ? Intersection<R> & (F extends unknown[] ? F[number] : F)
  : unknown;

Solution by JohnLi1999 #25898 

type Intersection<T extends any[]> = T extends [infer F, ...infer R] ?
  (F extends any[] ? F[number] : F) & Intersection<R> :
  unknown;

// old way
// type ToUnion<T extends any[]> = T[number];

// type Intersection<T extends any[]> = T extends [infer F, ...infer R] ?
//   (F extends any[] ? ToUnion<F> : F) & Intersection<R> :
//   unknown;

Solution by E-uler #24985 

type Intersection<T extends unknown[]> = T extends [ infer First, ...infer Rest]
? First extends unknown[]
  ? First[number] & Intersection<Rest>
  : First & Intersection<Rest>
: unknown

Solution by NeylonR #24535 

// your answers
type GetUnionIntersection<T, U> = T extends U ? T  : never 

type Intersection<T extends any[], Result = any> = 
T extends [infer F, ...infer R]
? Intersection<R, GetUnionIntersection<F extends number[] ? F[number] : F,Result>>
: Result

Solution by snakeUni #24032 

type GetUnionIntersection<T, U> = T extends U ? T  : never 

type Intersection<T extends any[], Result = any> = 
T extends [infer F, ...infer R]
? Intersection<R, GetUnionIntersection<F extends number[] ? F[number] : F,Result>>
: Result

Solution by TKBnice #23374 

type Intersection<T extends unknown[], R = unknown> =
  T extends [infer A, ...infer Rest]
    ? Intersection<Rest, R & (A extends unknown[] ? A[number] : A)>
    : R

Solution by drylint #22832 

type TupleToUnion<T> = T extends unknown[] ? T[number] : T

type Intersection<T> = 
  T extends [infer First, ...infer Rest]
    ? Rest extends []
      ? TupleToUnion<First>
      : Extract<TupleToUnion<First>, Intersection<Rest>>
    : never

playground

Solution by zhaoyao91 #21988 

// your answers
type Intersection<T, U = ''>
    = T extends [infer A, ... infer B]
    ? A extends any[]
    ? Intersection<[A[number], ...B], U>
    : Intersection<B, (U extends '' ? A : A & U)>
    : U

Solution by goddnsgit #21923 

// your answers
type Intersection<T extends any[], Ret = T[0]> =  T extends [infer First, ...infer Rest] ? Intersection<Rest, First extends any[] ? First[number] & (Ret extends any[] ? Ret[number] : Ret) : First & Ret>  : Ret

Solution by Rebornjiang #21806 

// your answers
type Intersection<T extends unknown[]> =
  T extends [ infer F, ...infer Rest]
    ? F extends unknown[]
      ? F[number] & Intersection<Rest>
      : F & Intersection<Rest>
    : unknown

Solution by YqxLzx #21676 

type Intersection<T extends Array<any>, ExtractValue = unknown> = T extends [
  infer A,
  ...infer B
]
  ? A extends Array<any>
    ? Intersection<B, Extract<A[number], ExtractValue>>
    : Intersection<B, Extract<A, ExtractValue>>
  : ExtractValue

Solution by so11y #21288 

type Intersection<T extends Array<any>, ExtractValue = unknown> = T extends [
  infer A,
  ...infer B
]
  ? A extends Array<any>
    ? Intersection<B, Extract<A[number], ExtractValue>>
    : Intersection<B, Extract<A, ExtractValue>>
  : ExtractValue

Solution by so11y #21287 

type Intersection<T extends unknown[]> = T extends [infer H, ...infer R]
  ? H extends readonly any[]
    ? H[number] & Intersection<R>
    : H & Intersection<R>
  : number;

Solution by JohannesSchwegler #20555 

type Intersection<T extends unknown[]> =
  T extends [ infer F, ...infer Rest]
    ? F extends unknown[]
      ? F[number] & Intersection<Rest>
      : F & Intersection<Rest>
    : unknown

Solution by lvjiaxuan #20335 

type ExculdeReversal<First, End> = First extends any[]
  ? End extends any[]
    ? Exclude<First[number], Exclude<First[number], End[number]>>
    : Exclude<First[number], Exclude<First[number], End>>
  : End extends any[]
  ? Exclude<First, Exclude<First, End[number]>>
  : Exclude<First, Exclude<First, End>>;

type Intersection<T extends unknown[], Last = unknown> = T extends [infer F, infer M, ...infer R]
  ? Intersection<R, ExculdeReversal<F, M>>
  : T extends [infer F1, ...infer R1]
  ? ExculdeReversal<Last, F1>
  : Last;

Solution by CaoXueLiang #19486 

type Intersection_Help_ArrayToUnion<T> = T extends any[] ? T[number] : T
type Intersection<T> = T extends [infer F, ...infer R]
  ? Intersection_Help_ArrayToUnion<F> & Intersection<R>
  : unknown

Solution by WongYAQi #17493

type TupleToUnion<T extends any[]> = T extends [infer el, ...infer rest] ? el | TupleToUnion : never; type FirstToUnion = T extends any[] ? T extends [infer el, ...infer rest] ? el | TupleToUnion : T : T; type ArrayToUnion<T extends any[], R extends any[] = []> = T extends [infer F, ...infer Rest] ? ArrayToUnion<Rest, [...R, FirstToUnion]> : R; type Intersection<T extends Array, R extends Array = ArrayToUnion, S extends any = R[0]> = R extends [infer F1, infer F2, ...infer Rest1] ? [Extract<F1, F2>] extends [never] ? never : Intersection<T, [Extract<F1, F2>, ...Rest1], Extract<F1, F2>> : S;

Solution by my5201314zwl #16866 

// your answers

type Intersection<T> = T extends [infer F, ...infer R]
  ? F extends unknown[]
    ? Extract<F[number], Intersection<R>>
    : Extract<F, Intersection<R>>
  : unknown

Solution by humandetail #16496 

// your answers
type Intersection<
    T extends readonly (number|number[])[],
    U extends number = number > =
    T extends [infer R extends number[],...infer S extends (number|number[])[]] 
    ? Intersection<S,Extract<R[number],U>>
    : T extends [infer R extends number,...infer S extends (number|number[])[]]
    ? Intersection<S,Extract<R,U>> 
    : U ;

Solution by justBadProgrammer #16002 

// your answers
type ArratToUnion<T extends unknown[], R extends unknown[] = []> = T extends [infer First, ...infer Rest]
? First extends unknown[]
  ? ArratToUnion<Rest, [...R, First[number]]>
  : ArratToUnion<Rest, [...R, First]>
: R

type X = ArratToUnion<[[1, 2], [3, 4], [5, 6]]>
type X1 = ArratToUnion<[[1, 2, 3], 2 | 3 | 4, 2 | 3]>
type Intersection<T extends unknown[]> = ArratToUnion<T> extends [infer First, infer Second, infer Third]
? First extends Second
  ? First extends Third
    ? First
    : never
  : never
: never

Solution by liuxing95 #13155 

// your answers

type ArrToUnion<T extends unknown[], R extends unknown[] = []> = T extends [infer First, ...infer Rest]
  ? [First] extends [unknown[]]
    ? ArrToUnion<Rest,[...R, First[number]]>
    : ArrToUnion<Rest,[...R, First]>
  : R

type Intersection<T extends unknown[]> = ArrToUnion<T> extends [infer First, infer Second, infer Third]
  ? First extends Second
    ? First extends Third
      ? First
      : never
    : never
  : never

Solution by GumplinGo #13042 

// your answers
type Intersection<T> = T extends [infer First, ...infer Rest]
  ? (First extends unknown[] ? First[number] : First) & Intersection<Rest>
  : unknown;

Solution by SeptEarlyMorning #12399 

type Intersection<T> = {[I in keyof T]: (_: T[I] extends (infer V)[] ? V : T[I]) => 1} extends 
    | Record<number, (_: infer I) => 1> ? I : never;

Playground

Solution by teamchong #11756 

type Extract<T> = T extends unknown[] ? T[number] : T

type Intersection<T extends unknown[]> = T extends [infer Head, ...infer Rest]
  ? Extract<Head> & Intersection<Rest>
  : unknown

Solution by adnasa #10717 

type Intersection<T, Res  = undefined> 
=
T extends [infer Start,...infer Other] ? 
Start extends any[] ? Res extends undefined ? Intersection<Other,Start[number]>: Intersection<Other, Extract<Res, Start[number]> >
:
 Intersection<Other, Extract<Res, Start> >: Res

Solution by EGyoung #8551 

type Intersection<T extends unknown[]> = T extends [infer F, ...infer R]
  ? (F extends unknown[] ? F[number] : F) & Intersection<R>
  : unknown

Solution by LoTwT #7780 

// your answers
// 塌ε₯—ηš„ζ•°η»„η±»εž‹ε±•εΌ€θ½¬ζˆunionη±»εž‹οΌŒη»„ζˆδΈ€δΈͺε…ƒη΄ ζ˜―unionηš„ζ•°η»„
type convertUnionArray<T extends unknown[], ResultArr extends unknown[] = []> =
  T extends [infer First, ...infer Rest]
    ? First extends unknown[]
      ? convertUnionArray<Rest, [...ResultArr, First[number]]>
    : convertUnionArray<Rest, [...ResultArr, First]>
  : ResultArr

  // δΊ€ε‰η±»εž‹
type Intersection<T extends any[], Union = convertUnionArray<T>[0]> = 
  convertUnionArray<T> extends [infer First, ...infer Rest]
    ? Intersection<Rest, Extract<First, Union>>
    : Union

Solution by HongxuanG #7343