// MARK: - 2006. Count Number of Pairs With Absolute Difference K

// Решение 1
func countKDifferenceOne(_ nums: [Int], _ k: Int) -> Int {
    var total = 0
    var dict = [Int:Int]()
    for value in nums {
        dict[value, default: 0] += 1
    }

    for value in nums {
        let diff = value - k
        if dict[diff] != nil {
            total += dict[diff]!
        }
    }
    return total
}
countKDifferenceOne([1,2,2,1], 1)

// Решение 2
func countKDifferenceTwo(_ nums: [Int], _ k: Int) -> Int {
    var total = 0
    var dict = [Int:Int]()
    for x in nums {
        total += (dict[x - k] ?? 0) + (dict[x + k] ?? 0)
        dict[x, default: 0] += 1
    }
    return total
}

countKDifferenceTwo([1,3], 3)