BFE.devAI解答 - TypeScript 类型谜题
62. implement Unique<T extends any[]>

type Unique<T extends Array<any>> = T extends [infer U, ...infer R]  ? U extends any    ? [U, ...Unique<Exclude<R, U>>]    : Unique<Exclude<R, U>>  : [];type A = Unique<['A', 'A', 'A', 'B', 'B', 'C']>;// A is resolved to ['A', 'A', 'A'] and R is resolved to ['B', 'B', 'C']// Unique<Exclude<R, 'A'>> becomes Unique<['B', 'B', 'C']> = ['B', 'C']// Resulting in ['A', ...['B', 'C']] = ['A', 'B', 'C']// Final output is ['A', 'B', 'C']

In the implementation of Unique, we use conditional types and recursion to remove duplicate elements from the input array. We extract the first element U from the array T, then recursively call Unique on the remaining elements R after excluding all occurrences of U. This process is repeated until all duplicate elements are removed, resulting in the deduplicated array.