FlattenDepth

介绍

递归摊平数组. 如果提供了深度, 应确保它是正数.

ts
type a = FlattenDepth<[1, 2, [3, 4], [[[5]]]], 2> // [1, 2, 3, 4, [5]]. flattern 2 times
type b = FlattenDepth<[1, 2, [3, 4], [[[5]]]]> // [1, 2, 3, 4, [[5]]]. Depth defaults to be 1

ts
type a = FlattenDepth<[1, 2, [3, 4], [[[5]]]], 2> // [1, 2, 3, 4, [5]]. flattern 2 times
type b = FlattenDepth<[1, 2, [3, 4], [[[5]]]]> // [1, 2, 3, 4, [[5]]]. Depth defaults to be 1

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起点

ts
/* _____________ Your Code Here _____________ */
 
type FlattenDepth<T> = any
 
/* _____________ Test Cases _____________ */
 
type cases = [
  Expect<Equal<FlattenDepth<[]>, []>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<FlattenDepth<[1, 2, 3, 4]>, [1, 2, 3, 4]>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<FlattenDepth<[1, [2]]>, [1, 2]>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<FlattenDepth<[1, 2, [3, 4], [[[5]]]], 2>, [1, 2, 3, 4, [5]]>>,
Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).2344
2314Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).  Expect<Equal<FlattenDepth<[1, 2, [3, 4], [[[5]]]]>, [1, 2, 3, 4, [[5]]]>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<FlattenDepth<[1, [2, [3, [4, [5]]]]], 3>, [1, 2, 3, 4, [5]]>>,
Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).2344
2314Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).  Expect<Equal<FlattenDepth<[1, [2, [3, [4, [5]]]]], 19260817>, [1, 2, 3, 4, 5]>>,
Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).2344
2314Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).]

ts
/* _____________ Your Code Here _____________ */
 
type FlattenDepth<T> = any
 
/* _____________ Test Cases _____________ */
 
type cases = [
  Expect<Equal<FlattenDepth<[]>, []>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<FlattenDepth<[1, 2, 3, 4]>, [1, 2, 3, 4]>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<FlattenDepth<[1, [2]]>, [1, 2]>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<FlattenDepth<[1, 2, [3, 4], [[[5]]]], 2>, [1, 2, 3, 4, [5]]>>,
Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).2344
2314Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).  Expect<Equal<FlattenDepth<[1, 2, [3, 4], [[[5]]]]>, [1, 2, 3, 4, [[5]]]>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.  Expect<Equal<FlattenDepth<[1, [2, [3, [4, [5]]]]], 3>, [1, 2, 3, 4, [5]]>>,
Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).2344
2314Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).  Expect<Equal<FlattenDepth<[1, [2, [3, [4, [5]]]]], 19260817>, [1, 2, 3, 4, 5]>>,
Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).2344
2314Type 'false' does not satisfy the constraint 'true'.
Generic type 'FlattenDepth' requires 1 type argument(s).]

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解决方案

Spoiler warning // Click to reveal answer

ts
// most popular
 
type FlattenDepth<
  T extends any[],
  S extends number = 1,
  U extends any[] = []
> = U['length'] extends S
  ? T
  : T extends [infer F, ...infer R]
  ? F extends any[]
    ? [...FlattenDepth<F, S, [...U, 1]>, ...FlattenDepth<R, S, U>]
    : [F, ...FlattenDepth<R, S, U>]
  : T

ts
// most popular
 
type FlattenDepth<
  T extends any[],
  S extends number = 1,
  U extends any[] = []
> = U['length'] extends S
  ? T
  : T extends [infer F, ...infer R]
  ? F extends any[]
    ? [...FlattenDepth<F, S, [...U, 1]>, ...FlattenDepth<R, S, U>]
    : [F, ...FlattenDepth<R, S, U>]
  : T

ts
// my solution
 
/**
 * 存在的问题: NumToArr由于19260817存在, 递归次数超过限制,产生ts报错. 所以当时硬编码了50次递归
 */
 
type NumToArr<N extends number = 1, U extends any[] = []> = N extends U['length']
  ? U
  : U['length'] extends 50
    ? U
    : NumToArr<N, [...U, N]>;
 
type NumMinusOne<T extends any[]> = T['length'] extends 1
  ? 0
  : T extends [infer F, ...infer Rest]
    ? Rest['length']
    :  0;
 
type desct<T extends any[], U extends any[] = []> = T extends [infer F, ...infer Rest]
  ? desct<Rest, [
      ...U,
      ...(F extends any[] ? F : [F])
    ]>
  : U;
 
 
  type FlattenDepth<T extends any[], D extends number = 1, U extends any[] = T> = D extends 0 
  ? U 
  : FlattenDepth<desct<U>, NumMinusOne<NumToArr<D, []>>>;

ts
// my solution
 
/**
 * 存在的问题: NumToArr由于19260817存在, 递归次数超过限制,产生ts报错. 所以当时硬编码了50次递归
 */
 
type NumToArr<N extends number = 1, U extends any[] = []> = N extends U['length']
  ? U
  : U['length'] extends 50
    ? U
    : NumToArr<N, [...U, N]>;
 
type NumMinusOne<T extends any[]> = T['length'] extends 1
  ? 0
  : T extends [infer F, ...infer Rest]
    ? Rest['length']
    :  0;
 
type desct<T extends any[], U extends any[] = []> = T extends [infer F, ...infer Rest]
  ? desct<Rest, [
      ...U,
      ...(F extends any[] ? F : [F])
    ]>
  : U;
 
 
  type FlattenDepth<T extends any[], D extends number = 1, U extends any[] = T> = D extends 0 
  ? U 
  : FlattenDepth<desct<U>, NumMinusOne<NumToArr<D, []>>>;

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FlattenDepth

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解决方案​

介绍

起点

解决方案