Type Challenges: 30301-medium-isodd Solution

type Odd = 1 | 3 | 5 | 7 | 9;

type IsOdd<T extends number> =
  `${T}` extends `${string}.${string}`
    ? false
    : `${T}` extends `${infer F extends number}e${infer R extends number}`
        ? R extends 0
          ? IsOdd<F>
          : false
      : `${T}` extends `${number | ''}${Odd}`
        ? true
        : false;

Consider cases where the exponent of e is 0. example, 3e0 = 3×10^0= 3×1 = 3 = odd. but 2e0 = 2×10^0 = 2×1 = 2 = even.

Solution by ysknsid25 #35226

type IsOdd<T extends number> =
  `${T}` extends `${infer _}${1 | 3 | 5 | 7 | 9}`
    ? true
    : false

Solution by drylint #34178

type Last<T extends string> = T extends `${infer R}${infer last}` ? last extends '' ? R : Last<last> : never
type IsOdd<T extends number> = `${T}` extends `${string}${'.' | 'e'}${string}` ? false : Last<`${T}`> extends `${1 | 3 | 5 | 7 | 9}` ? true : false

Solution by ouzexi #34173

type IsOdd<T extends number> = number extends T 
  ? false 
  : `${T}` extends `${number}.${number}` | `${number}${0|2|4|6|8}` | `${number}e${number}`
    ? false 
    : true

Solution by ruslauz #33812

type IsOdd<T extends number> =  `${T}` extends `${bigint | ''}${1 | 3 | 5 | 7 | 9}` ? true : false;

Solution by sunupupup #33491

type IsOdd<T extends number>
  = `${T}` extends `${any}e${any}` | `${any}.${any}` ? false
  : `${T}` extends `${any}${1 | 3 | 5 | 7 | 9}` ? true : false

Playground

Solution by teamchong #32994

type OddNumbers = '1' | '3' | '5' | '7' | '9'

type GetLastDigit<T extends number | string, Acc extends string = ""> = `${T}` extends `${infer F}${infer R}`
  ? GetLastDigit<R, F>
  : Acc

type IsExpo<T extends number> = `${T}` extends `${number}e${number}`
  ? true
  : false

type IsDecimal<T extends number> = `${T}` extends `${number}.${number}`
  ? true
  : false

type IsOdd<T extends number> =  IsExpo<T> extends true
  ? false 
  : IsDecimal<T> extends true
    ? false
    : GetLastDigit<T> extends OddNumbers
      ? true
      : false

Solution by keyurparalkar #32884

type OddNumbers = '1' | '3' | '5' | '7' | '9'

type GetLastDigit<T extends number | string, Acc extends string = ""> = `${T}` extends `${infer F}${infer R}`
  ? GetLastDigit<R, F>
  : Acc

type IsExpo<T extends number> = `${T}` extends `${number}e${number}`
  ? true
  : false

type IsDecimal<T extends number> = `${T}` extends `${number}.${number}`
  ? true
  : false

type IsOdd<T extends number> =  IsExpo<T> extends true
  ? false 
  : IsDecimal<T> extends true
    ? false
    : GetLastDigit<T> extends OddNumbers
      ? true
      : false

Solution by keyurparalkar #32883

type Odd = 1 | 3 | 5 | 7 | 9;
type IsOdd<T extends number> = `${T}` extends `${string}${Odd}` ? true : false;

Solution by Vampirelee #32595

type IsOdd<T extends number> = `${T}` extends `${string}${1 | 3 | 5 | 7 | 9}`
  ? true
  : false;

Solution by vangie #32194

type Odd = '1' | '3' | '5' | '7' | '9';
type IsOdd<T extends number> = `${T}` extends `${string}${Odd}` ? true : false;

Solution by bigcreate #31216

type IsOdd<T extends number> = `${T}` extends `${infer _}${1 | 3 | 5 | 7 | 9}` ? true : false

Solution by milletlovemouse #31083

type GetLastChar<
  T extends number,
  U extends string = `${T}`
> = U extends `${infer F}${infer R}`
  ? R extends ""
    ? F extends `${infer Res extends number}`
      ? Res
      : F
    : GetLastChar<T, R>
  : T;

type IsOdd<
  T extends number,
  D extends number = GetLastChar<T>,
  U extends any[] = [],
  F extends boolean = false
> = U["length"] extends D
  ? F
  : IsOdd<T, D, [...U, 0], F extends false ? true : false>;

Solution by moonpoet #31059

type MakeArray<T extends number | string, U extends unknown[] = []> = `${U['length']}` extends `${T}`
  ? U
  : MakeArray<T, [...U, unknown]>;

type oddNumber = 1 | 3 | 5 | 7 | 9;

type LastString<S extends string> = S extends `${infer F}${infer L}` ? (L extends '' ? F : LastString<L>) : S;

type IsOdd<T extends number, U extends unknown[] = MakeArray<LastString<`${T}`>>> = U['length'] extends oddNumber
  ? true
  : false;

Solution by leejaehyup #30945

type IsOdd<T extends number> = `${T}` extends `${any}${'1' | '3' | '4' | '7' | '9'}` ? true : false

Solution by DevilTea #30908

type Num2Arr<T extends number | string> = `${T}` extends `${infer A}${infer B}` ? [A, ...Num2Arr<B>] : []
type IsOdd<T extends number> = number extends T ? false : Num2Arr<T> extends [...infer A, infer B] ? B extends '1' | '3' | '5' | '7' | '9' ? true : false : false

Solution by dreamluo-plus #30716

type LastWord<T extends string> = T extends `${infer F}${infer R}`
  ? R extends ''
    ? F
    : LastWord<R>
  : never;

type IsOdd<T extends number> = LastWord<`${T}`> extends '1' | '3' | '5' | '7' | '9' ? true : false

Solution by XkSuperCool #30341

// your answers
type IsOdd<T extends number> =  `${T}` extends `${number | ''}${1 | 3 | 5 | 7 | 9}` ? true : false;

Solution by omittee #30334

// your answers

type OddNume = "1" | "3" |"5" | "7" |"9"
type GetTheLastNumber<T extends string> = T extends `${infer F}${infer L}` ? L extends "" ? F : GetTheLastNumber<L> : never
type IsOdd<T extends number> = GetTheLastNumber<`${T}`> extends OddNume ? true : false

Solution by kerolossamir165 #30328


type Odd = 1 | 3 | 5 | 7 | 9;
type Last<T extends string> = T extends `${any}${infer S}${infer R}` ? Last<`${S}${R}`> : T;

type IsOdd<T extends number> = Last<`${T}`> extends `${Odd}` ? true : false;

// other way
// type Last<T extends string> = T extends `${any}${infer S}${infer R}` ? Last<`${S}${R}`> : T;

// type IsOdd<T extends number, _SWITCH extends boolean = false, _Counter extends 1[] = []> =
//   `${_Counter[`length`]}` extends Last<`${T}`> ? _SWITCH /*return*/ :
//   IsOdd<T, _SWITCH extends true ? false : true, [..._Counter, 1]>;


// simple way
// type IsOdd<T extends number> = `${T}` extends `${number}${1 | 3 | 5 | 7 | 9}` ? true : false;

simple way : https://github.com/type-challenges/type-challenges/issues/30334#issue-1929313282

Solution by E-uler #30324

type ToString<T extends number> = `${T}`
type LastDigit<T extends string> = 
T extends `${infer F}${infer L}`?
  L extends ""?
    F:LastDigit<L>
  :never

type Match<T extends string> = T extends '1' | '3' | '5' | '7' | '9'?true:false

type IsOdd<T extends number> = Match<LastDigit<ToString<T>>>

Solution by jiangshanmeta #30303