Trace

约 141 字小于 1 分钟

2026-02-11

题目

The trace of a square matrix is the sum of the elements on its main diagonal. However, it's difficult to calculate the sum with type system. To make things simple, let's return the elements on the main diagonal with union type.

For example:

type Arr = [
  [1,2],
  [3,4]
]
type Test = Trace<Arr> // expected to be 1 | 4

解题思路

待补充

答案

type Trace<T extends any[][]> = any

验证

import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<Trace<[[1, 2], [3, 4]]>, 1 | 4>>,
  Expect<Equal<Trace<[[0, 1, 1], [2, 0, 2], [3, 3, 0]]>, 0>>,
  Expect<Equal<Trace<[['a', 'b', ''], ['c', '', ''], ['d', 'e', 'f']]>, 'a' | '' | 'f'>>,
]

参考

无