export function countPairsWithDiffK(numbers: number[], k: number): number {

  let result = 0

  if (k === 0) {

    const occurrences = new Map<number, number>()
    numbers.forEach(n => occurrences.set(n, (occurrences.get(n) || 0) + 1))

    let duplicates = 0
    for (const value of occurrences.values()) {
      duplicates += value >= 2 ? 1 : 0
    }
    result = duplicates

  } else {

    const uniqueNums = new Set<number>(numbers)
    let count = 0

    for (const num of uniqueNums.values()) {
      count += uniqueNums.has(num + k) ? 1 : 0
    }

    result = count

  }

  return result
}