self.intersection for ruby_game

[CodeOfficer]

Great presentations this eve, thanks Casey and Renae. I had a blast!

I thought I'd post this here for anyone who didn't record the link of
the github repo. I just committed the code Bogart I and I worked on.

http://github.com/clr/ruby_games/tree/master

Here are the 4 examples we came up with, the last being the
fastest ... 9 times slower than the (array_1 & array_2) approach.

class IntegerArray

def self.intersection( array_1, array_2 )
# ----------------------------
# Completed by
# Russ Jones and Bogart Salzberg
# ----------------------------

# ----------------------------
# way #1
# 0.020000 0.000000 0.020000 ( 0.026530)
# 502.560000 0.820000 503.380000 (503.767833)
# Finished in 503.796304 seconds (8.3 minutes - 18988 x slower)
# ----------------------------

# array_3 = []
# array_1.each do |x|
# array_3 << x if array_2.include? x
# end
# array_3

# ----------------------------
# way #2
# 0.020000 0.000000 0.020000 ( 0.027828)
# 505.350000 0.940000 506.290000 (506.756947)
# Finished in 506.786922 seconds (8.4 minutes - 18210 x slower)
# ----------------------------

# array_1.reject! do |item|
# !array_2.include? item
# end

# ----------------------------
# way #3
# 0.020000 0.000000 0.020000 ( 0.027342)
# 513.080000 0.860000 513.940000 (514.371741)
# Finished in 514.40147 seconds (8.5 minutes - 18812 x slower)
# ----------------------------

# array_1.delete_if { |item| !array_2.include? item }

# ----------------------------
# way #4
# 0.020000 0.000000 0.020000 ( 0.028825)
# 0.270000 0.000000 0.270000 ( 0.271256)
# Finished in 0.302076 seconds (only 9 times slower)
# ----------------------------

array_1.sort!
array_2.sort!
array_3 = []
index_1 = 0
index_2 = 0

while true
break if (array_1[index_1]==nil || array_2[index_2]==nil)
case array_1[index_1] <=> array_2[index_2]
when -1
# less than
index_1 += 1
when 1
# greater than
index_2 += 1
else
# equal
array_3 << array_1[index_1]
index_1 += 1
index_2 += 1
end
end

array_3
end

end