From: "Llelan D." <lists@...>
Date: 2012-05-17T09:56:54+09:00
Subject: Re: Ruby Arrays (Pushing Array Inside the same array)

The main problem here is the description of what is desired. A lot of
information has been left out. An analysis of the given input and output
arrays would seem to suggest the algorithm:

c << a[i] and d << b[i] if
       a[i] is not a multiple of a[j] from any other element
    && b[i] != b[j]

The unanswered questions are
    Is there a pattern to the sequence of x values? Those given are
ascending multiples of 9.
    What is the relationship of b[i] to a[i]?

The following ruby implementation performs the above algorithm with no
assumption about the pattern or order of elements in array a, or the
relationship of b[i] to a[i].
--------------------------------------------------------------------
a, b, c, d =
    [9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99, 108, 117, 126],
    [1,  1,  2,  1,  1,  3,  4,  5,  2,  1,  1,   3,   6,   1],
    [],
    []

(a.count - 1).times {|i|
    (ai, bi) = a[i], b[i]
    ej = (a.count - 1).times
    loop do
        begin
            j = ej.next
            (aj, bj) = a[j], b[j]
            break if i != j and ai % aj == 0 and bi == bj
        rescue
            c << ai
            d << bi
            break
        end
    end
}
c << a[-1]
d << b[-1]

puts('c: ' + c.to_s)
puts('d: ' + d.to_s)
--------------------------------------------------------------------
Output:

c: [9, 27, 54, 63, 72, 117, 126]
d: [1, 2, 3, 4, 5, 6, 1]
--------------------------------------------------------------------

It may not be the most concise usage of the Ruby syntax, but it gets the
job done without generating any extra array copies, and terminates the
inner loop once a reason is found to not push the current (ai, bi) pair.

If more were known about the pattern of values in a, or the relationship
of b[i] to a[i], a more efficient implementation could be created.

You might find it more friendly to Ruby to change the input values from
two separate arrays with the same length to one array with 2-element
pairs as elements. [[9, 1], [18, 1]...]

I hope you find that of some help.

P.S. If anyone can create the same implementation with more concise Ruby
syntax without generating any extra interim arrays, I'd love to see it.

-- 
Posted via http://www.ruby-forum.com/.