31

I have 2 arrays:

@array1 = [a,b,c,d,e]
@array2 = [d,e,f,g,h]

I want to compare the two arrays to find matches (d,e) and count the number of matches found (2)?

<% if @array2.include?(@array1) %>
  # yes, but how to count instances?
<% else %>
  no matches found...
<% end %>

Thanks in advance~

Nakilon
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thedeepfield
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3 Answers3

81

You can do this with array intersection:

@array1 = ['a', 'b', 'c', 'd', 'e']
@array2 = ['d', 'e', 'f', 'g', 'h']
@intersection = @array1 & @array2

@intersection should now be ['d', 'e']. You can then do the following:

<% if !@intersection.empty? %>
  <%= @intersection.size %> Matches Found.
<% else %>
  No Matches Found.
<% end %>
Pan Thomakos
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1

To find the number of total matches between the arrays, add them together, then subtract the unique set. The difference between the length of the superset array and the uniq set will be the count of the matches of the second array in the first. This method works best if a2 is a unique set.

a1 = ['a','b','c','d','d','d']
a2 = ['a','d']

superset = (a1 + a2)
subset = superset.uniq

matches = superset.count - subset.count
vanboom
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0
class Array
  def dup_hash
    inject(Hash.new(0)) { |h,e| h[e] += 1; h }.select { 
      |k,v| v > 1 }.inject({}) { |r, e| r[e.first] = e.last; r }
  end
end

First you just add both arrays

@array_sum = @array1 + @array2

output = [a,b,c,d,e,d,e,f,g,h]

@array_sum.dub_hash => {d => 2, e => 2}

Or check this How to count duplicates in Ruby Arrays

Community
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kriysna
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