2059 - Drop String

[justBadProgrammer]

// your answers
type StringToUnion<
    S extends string,
    T extends readonly string[] =[]> =
    S extends `${infer R extends string}${infer U extends string}`
    ? StringToUnion<U,[...T,R]>
    : T[number] ;

type DropString<
    S extends string, 
    R extends string,
    U extends string=StringToUnion<R> > = 
    S extends `${infer V extends string}${infer W extends string}`
    ? V extends U
    ? DropString<W,R>
    :`${V}${DropString<W,R>}`
    : ''  ;