tests/performance/nested_loop/base/search.ts

export function findDuplicates(items: string[]): string[] {
  const seen = new Set<string>()
  const duplicates: string[] = []

  for (const item of items) {
    if (seen.has(item)) {
      duplicates.push(item)
    }
    seen.add(item)
  }

  return duplicates
}