25270 - Transpose

[sunupupup]

A very blunt solution ...

type InitRetItems<
  M extends number[][],
  Ret extends number[][] = []
> = Ret['length'] extends M[0]['length'] ? Ret : InitRetItems<M, [[], ...Ret]>;

type RemoveFirstItem<Arr extends any[]> = Arr extends [any, ...infer Rest]
  ? Rest
  : [];

// append every line
type AppendEveryLine<
  Line extends number[],
  Ret extends number[][]
> = Line extends [infer FirstNum, ...infer Rest extends number[]]
  ? [[...Ret[0], FirstNum], ...AppendEveryLine<Rest, RemoveFirstItem<Ret>>]
  : [];

type Transpose<
  M extends number[][],
  Ret extends number[][] = InitRetItems<M>
> = M extends [infer Arr extends number[], ...infer Rest extends number[][]]
  ? Transpose<Rest, AppendEveryLine<Arr, Ret>>
  : Ret;

[sunupupup]

very concise solution

type Transpose<
  M extends number[][],
  Ret = M["length"] extends 0 ? [] : M[0]  //初始化数组长度
> = {
  [X in keyof Ret]: {
    [Y in keyof M]: X extends keyof M[Y] ? M[Y][X] : never
  }
}