Type Challenges: 09142-medium-checkrepeatedchars Solution

type CheckRepeatedChars<T extends string, A extends any[] = []> = T extends `${infer F}${infer Rest}`
  ? F extends A[number]
    ? true
    : CheckRepeatedChars<Rest, [...A, F]>
  : false;

Solution by wendao-liu #35094

// your answers
type CheckRepeatedChars<T extends string, A extends string[]  = []> = T extends `${infer F}${infer L}` ? F extends A[number] ? true : CheckRepeatedChars<L, [F, ...A]>  : false

Solution by gobielJonathan #34536

// if T includes S, return true
type Includes<T extends string, S extends string> = T extends `${infer F}${infer R}`
  ? Equal<F, S> extends true
    ? true
    : Includes<R, S>
  : false;

// produce unique characters of type parameter S
type Unique<S extends string> = S extends `${infer F}${infer R}`
  ? Includes<R, F> extends true
    ? Unique<R>
    : `${F}${Unique<R>}`
  : "";

type StringToTuple<S extends string> = S extends `${infer F}${infer R}`
  ? [F, ...StringToTuple<R>]
  : [];

type CheckRepeatedChars<T extends string> = StringToTuple<T>["length"] extends StringToTuple<
  Unique<T>
>["length"]
  ? false
  : true;

Solution by yukicountry #34347

type CheckRepeatedChars<T extends string> = T extends `${infer R}${infer rest}` ? (rest extends `${string}${R}${string}` ? true : CheckRepeatedChars<rest>) : false

Solution by ouzexi #34107

type UnionToIntersection<U> = (U extends U ? (k: U) => 0 : never) extends (k: infer I) => 0 ? I : never
type LastUnion<U> = UnionToIntersection<
  (U extends U ? (k: U) => 0 : never)
> extends (k: infer I) => 0 ? I : never
type UnionToTuple<T> = [T] extends [never] ? [] : [...UnionToTuple<Exclude<T, LastUnion<T>>>, LastUnion<T>]
type UnionLength<T> = UnionToTuple<T>['length']

type CheckRepeatedChars<T extends string> 
= StrToArr<T>['length'] extends UnionLength<StrToUnion<T>>
    ? false 
    : true

Solution by ScriptBloom #33960

type isEqual<T, U> = (<G>() => G extends T ? 1 : 2) extends (<G>() => G extends U ? 1 : 2) ? true : false

type Includes<T extends any[], U> = T extends [infer First, ...infer Rest] ? isEqual<First, U> extends true ? true : Includes<Rest, U> : false

type CheckRepeatedChars<T extends string, Tuple extends any[] = []> = T extends `${infer First}${infer Rest}` ? CheckRepeatedChars<Rest, [...Tuple, First]> 
: Tuple extends [infer F, ...infer R]
  ? Includes<R, F> extends true
    ? true
    : CheckRepeatedChars<'', R>
  : false

Solution by PiligrimStas #33796

first_char extends pre_chars_union


type CheckRepeatedChars<S extends string, U = ''> = 
S extends `${infer Char}${infer Rest}` 
  ? Char extends U ? true :  CheckRepeatedChars<Rest, U | Char>
  : false

Solution by sunupupup #33438

// your answers
type CheckRepeatedChars<T extends string> = T extends `${infer L}${infer R}`
? R extends `${infer _}${L}${infer _}`
  ? true : CheckRepeatedChars<R>
: false

Solution by pea-sys #33226

type StringToTuple<T extends string, Acc extends string[] = []> = T extends `${infer F}${infer R}`
  ? StringToTuple<R, [...Acc, F]>
  : Acc

type CheckRepeatedChars<T extends string> = T extends `${infer F}${infer R}`
    ? F extends StringToTuple<R>[number]
      ? true
      : CheckRepeatedChars<R>
    : false

Solution by keyurparalkar #32651

type CheckRepeatedChars<
  T extends string,
  S extends string[] = []
> = T extends `${infer F}${infer R}`
  ? F extends S[number]
    ? true
    : CheckRepeatedChars<R, [...S, F]>
  : false;

Solution by vangie #32191

type StringToUnion<S extends string, V extends any[] = []> = S extends `${infer First}${infer Rest}`
  ? StringToUnion<Rest, [...V, First]>
  : V[number];

type CheckRepeatedChars<T extends string> = T extends `${infer F}${infer Rest}`
  ? F extends StringToUnion<Rest>
    ? true
    : CheckRepeatedChars<Rest>
  : false;

Solution by leejaehyup #30862

type CheckRepeatedChars<T extends string, U extends any[] = []> = T extends `${infer A}${infer B}` ? A extends U[number] ? true : CheckRepeatedChars<B, [...U, A]> : false

Solution by dreamluo-plus #30682

将S转为Union，之后从Union中递归排除S，当S extends ''并且[Union] extends never时则为false反之为true

type StringToUnion<S extends string> = S extends `${infer L}${infer R}` ? L | StringToUnion<R> : never;
type CheckRepeatedChars<S extends string, U = StringToUnion<S>> =
  [U] extends [never] 
    ? S extends '' 
      ? false : true
    : S extends `${infer L}${infer R}`
      ? CheckRepeatedChars<R, Exclude<U, L>> : never

Solution by sv-98-maxin #30123

定义一个前缀数组，然后开始遍历字符串，检查每个字符是否存在于前缀数组中，存在即返回false，不存在则继续遍历。当遍历完整个字符串，即返回true。

type CheckRepeatedChars<T extends string, Prefix extends string[]= []> =
T extends `${infer F}${infer R}`
? F extends Prefix[number]
  ? true
  : CheckRepeatedChars<R, [...Prefix, F]>
: false

Solution by stevenaces #29421

type CheckRepeatedChars<
  T extends string,
  U extends string = ""
> = T extends `${infer F}${infer R}`
  ? F extends U
    ? true
    : CheckRepeatedChars<R, U | F>
  : false;

Solution by DoubleWoodLin #28841

来解新题了，好久没写了。

利用字符串解构，把 T 拆分成前缀 F 和后缀 E，按照从前往后的遍历，如果后缀 E 中包含前缀 F 则表示存在相同字符，如果不包含则递归后缀 E

type CheckRepeatedChars<T extends string> = T extends `${infer F}${infer E}` 
  ? E extends `${string}${F}${string}`
    ? true
    : CheckRepeatedChars<E>
  : false

Solution by linjunc #28150

type CheckRepeatedChars<T extends string> =
  // 匹配第一个子字符X和后面所有的子字符Y
  T extends `${infer X}${infer Y extends string}`
    ? // 通过字符Y去匹配是否存在子字符X，如果存在则有重复
      Y extends `${infer A}${X}${infer B}`
      ? true
      : CheckRepeatedChars<Y>
    : false;

Solution by jiaowoxiaobala #27905

type StoTuple<T extends string> = T extends `${infer F}${infer R}`
  ? [F, ...StoTuple<R>]
  : []

type C<T extends string[]> = T extends [infer F, ...infer R extends string[]]
  ? F extends R[number]
    ? true
    : C<R>
  : false

type CheckRepeatedChars<T extends string> = C<StoTuple<T>>

Solution by jazelly #27562

type CheckRepeatedChars<T extends string> =
  T extends `${infer A}${infer Rest}`
    ? Rest extends `${infer _}${A}${infer _}`
      ? true
      : CheckRepeatedChars<Rest>
    : false

Solution by drylint #27399

type CheckRepeatedChars<
  T extends string,
  A extends string[] = []
> = T extends `${infer H}${infer R}`
  ? H extends A[number]
    ? true
    : CheckRepeatedChars<R, [...A, H]>
  : false

Solution by HydenLiu #27356

// 辅助函数 判断指定字符串是否重复
type IsRepeated<T extends string, U extends string, M extends any[] = []> =
  T extends `${infer L}${infer R}` ?
  U extends L ? IsRepeated<R, U, [...M, L]> : IsRepeated<R, U, M>
  : M['length'] extends 1 ? false : true

// 结果
type CheckRepeatedChars<T extends string, O extends string = T> = 
T extends `${infer L}${infer R}` 
? IsRepeated<O, L> extends true ? true : CheckRepeatedChars<R, O> : false

Solution by wuxin0011 #27339

type CheckRepeatedChars<T extends string, B extends boolean = false> = 
  T extends `${infer F}${infer R}` 
  ? R extends `${string}${F}${string}` 
    ? true 
    : CheckRepeatedChars<R, B> 
  : B

Solution by smileboyi #27193

type StringToTuple<S extends string> = S extends `${infer F extends string}${infer Rest}` 
  ? F | StringToTuple<Rest> 
  : never

type CheckRepeatedChars<T extends string, F extends string = ''> = 
  T extends `${F}${infer S extends string}${infer Rest extends string}` 
    ? S extends StringToTuple<`${F}${Rest}`> 
      ? true
      : CheckRepeatedChars<T, `${F}${S}`>
    : false

Solution by Minato1123 #27069

type OneByString<T extends string,U extends string> = T extends `${infer S}${infer R}` ? S extends U ? true : OneByString<R,U> : false
type CheckRepeatedChars<T extends string> = T extends `${infer S}${infer R}` ? OneByString<R,S> extends true ? true : CheckRepeatedChars<R> : false

Solution by WangZiChu199910252255 #26901

type CheckRepeatedChars<T extends string> = T extends `${infer F}${infer R}` ? R extends `${any}${F}` ? true : CheckRepeatedChars<R> : false

Solution by owenvip #26745

type StringToUnion<S extends string> = S extends `${infer F}${infer Str}`
  ? F | StringToUnion<Str>
  : never

type CheckRepeatedChars<T extends string> = T extends `${infer F}${infer Str}`
  ? F extends StringToUnion<Str>
    ? true
    : CheckRepeatedChars<Str>
  : false

Solution by XkSuperCool #26293

// 你的答案
type CheckRepeatedChars<T extends string> = 
  T extends `${infer X}${infer Y extends string}`
    ? Y extends `${infer A}${X}${infer B}`
      ? true 
      : CheckRepeatedChars<Y>
    : false

Solution by kiki-zjq #25763

type CheckRepeatedChars<T extends string> = T extends `${infer First}${infer Rest}`
? Rest extends `${string}${First}${string}`
  ? true
  : CheckRepeatedChars<Rest>
: false

Solution by NeylonR #24929

type CheckRepeatedChars<
  T extends string,
  A extends string = never
> =
T extends `${infer F}${infer R}`?
  F extends A?
    true:CheckRepeatedChars<R, A | F>
  :false

Solution by jiangshanmeta #24835

type CheckRepeatedChars<T extends string, U = never> = T extends `${infer P}${infer R}`
? P extends U 
  ? true
  : CheckRepeatedChars<R, U | P>
: false

Solution by echizen #24734