2sum

# 2sum drill

function main(x::Array{Int64, 1}, y::Int64)
    n = length(x)
    z = Array{Int64}(undef, n, 2)
    h = Array{UInt64}(undef, n)
    c = 0

    for i = 1:n
        xx = y - x[i]

        if xx in x
            temp = [x[i], xx]
            temp_ = [xx, x[i]]

            if !(hash(temp) in h[1:c]) && !(hash(temp_) in h[1:c])
                c += 1
                z[c,:] = temp
                h[c] = hash(temp)
            end
        end
    end

    if c > 0
        return z[1:c,:]
    else
        println("no pairs found!")
    end
end