// MARK: - Скалярное произведение сжатых векторов

struct CompressedBlock {
    var value: Int64
    var count: Int
}

func dotProduct(lhs: [CompressedBlock], rhs: [CompressedBlock]) -> Int64 {
    var result: Int64 = 0

    var lhsBlock = CompressedBlock(value: 0, count: 0)
    var rhsBlock = CompressedBlock(value: 0, count: 0)

    var lhsIndex = 0
    var rhsIndex = 0

    while lhsIndex < lhs.count || rhsIndex < rhs.count {
        if lhsBlock.count == 0 {
            lhsBlock = lhs[lhsIndex]
            lhsIndex += 1
        }
        if rhsBlock.count == 0 {
            rhsBlock = rhs[rhsIndex]
            rhsIndex += 1
        }

        let commonCount = min(lhsBlock.count, rhsBlock.count)
        result += Int64(commonCount) * lhsBlock.value * rhsBlock.value
        lhsBlock.count -= commonCount
        rhsBlock.count -= commonCount
    }

    return result
}

let vectorA = [CompressedBlock(value: 1, count: 3)]
let vectorB = [CompressedBlock(value: 1, count: 2), CompressedBlock(value: 10, count: 1)]

dotProduct(lhs: vectorA, rhs: vectorB)