From: Dan <dandiebolt@...>
Date: 2009-08-25T01:22:57+09:00
Subject: INNER JOINING Two Arrays

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I have two arrays a and b which I need to iterate through simultaneously cr=
eating essentially an "INNER JOIN" on the values of the two arrays. Both ar=
rays contain integers and are sorted in ascending order. The first value in=
 each array is the same and the last value in each array is the same. On ea=
ch iteration through the arrays I need to obtain the indexes of each array =
if the array values are equal to each other.

This is the code I have which works:

a=3D[1,2,5,13]
b=3D[1,1,2,2,2,5,13,13,13]

indexs=3D[]
items=3D[]
a.each_with_index do |itema,indexa|
=A0b.each_with_index do |itemb,indexb|
=A0 if (itema=3D=3Ditemb) then
=A0=A0 puts "#{indexa} #{indexb}"
=A0=A0 indexs << [indexa,indexb]
=A0=A0 items=A0 << [itema,itemb]
=A0 else=20
=A0=A0 next
=A0 end
=A0end
end

producing this output:

0 0
0 1
1 2
1 3
1 4
2 5
3 6
3 7
3 8

and these values of indexs and items:

irb(main):017:0> indexs
=3D> [[0, 0], [0, 1], [1, 2], [1, 3], [1, 4], [2, 5], [3, 6], [3, 7], [3, 8=
]]

irb(main):018:0> items
=3D> [[1, 1], [1, 1], [2, 2], [2, 2], [2, 2], [5, 5], [13, 13], [13, 13], [=
13, 13]]

Q1: Is there a more idiomatic and concise way of doing this using functiona=
l array methods?=A0=20

Also note that if you interchanged the two each loops they would produce th=
e same output and results:

b.each_with_index do |itemb,indexb|
=A0a.each_with_index do |itema,indexa|
=A0 ...
=A0end
end

Q2: Are there any observations one could make about which scenario would be=
 faster both for my code and a more idiomatic solution you might have?

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