cpp2DArrFillByMult2

#include <iostream>

int main()
{
    const int mult{ 2 };
    const int sizeY{ 3 };
    const int sizeX{ 4 };
    int arr[sizeY][sizeX];

    std::cout << "Enter starting value:\n";
    std::cin >> arr[0][0];

    for (int y{ 0 }; y < sizeY; ++y)
    {
        std::cout << arr[y][0] << '\t';
        for (int x{ 1 }; x < sizeX; ++x)
        {
            std::cout  << (arr[y][x] = arr[y][x - 1] * mult) << '\t';
        }
        std::cout << '\n';
        if (y < sizeY - 1) { arr[y + 1][0] = arr[y][sizeX - 1] * mult; }
    }
    return 0;
}