Integers Comparator

题目来源(type-challenges)

问题 #

实现类型级整数比较器。 我们提供了一个枚举来指示比较结果, 例如:

• 如果 a 比 b 大, 则应该是 Comparison.Greater.
• 如果 a 和 b 相等, 则应该是 Comparison.Equal.
• 如果 a 比 b 小, 则应该是 Comparison.Lower.

请注意 a 和 b 可以是正整数或者负数和0, 也可能一正一负.

type case1 = Comparator<5, 5>// Comparison.Equal
type case2 = Comparator<5, 6>// Comparison.Lower
type case3 = Comparator<5, 8>// Comparison.Lower
type case4 = Comparator<5, 0>// Comparison.Greater
type case5 = Comparator<-5, 0>// Comparison.Lower
type case6 = Comparator<0, 0>// Comparison.Equal
type case7 = Comparator<0, -5>// Comparison.Greater
type case8 = Comparator<5, -3>// Comparison.Greater
type case9 = Comparator<5, -7>// Comparison.Greater
type case10 = Comparator<-5, -7>// Comparison.Greater
type case11 = Comparator<-5, -3>// Comparison.Lower
type case12 = Comparator<-25, -30>// Comparison.Greater
type case13 = Comparator<15, -23>// Comparison.Greater
type case14 = Comparator<40, 37>// Comparison.Greater
type case15 = Comparator<-36, 36>// Comparison.Lower
type case16 = Comparator<27, 27>// Comparison.Equal
type case17 = Comparator<-38, -38>// Comparison.Equal

解答 #

type Tuple<T extends string | number, Res extends unknown[] = []> = `${Res['length']}` extends `${T}` ? Res : Tuple<T, [...Res, 1]>
type Sub<A extends string | number, B extends string | number> = Tuple<A> extends [...Tuple<B>, ...infer Rest] ? Rest['length'] : false

enum Comparison {
  Greater,
  Equal,
  Lower,
}

type Comparator<A extends number, B extends number> =
A extends B
  ? Comparison.Equal
  : `${A}` extends `-${infer NA}`
    ? `${B}` extends `-${infer NB}`
      ? Sub<NA, NB> extends false ? Comparison.Greater : Comparison.Lower
      : Comparison.Lower
    : `${B}` extends `-${infer _}`
      ? Comparison.Greater
      : Sub<A, B> extends false ? Comparison.Lower : Comparison.Greater

拆分 #

• 判断是否相等
• 根据一正一负直接返回结果
• 接下来根据两数相减返回结果