Ruby - Checking if one array key/value is NOT present in another one-CodePudding

With ruby, I am trying to look from the first array key[:nb].value, if there is NOT one similar pair in the second one.

Considerate below arrays contain thousands of elements:

arr1 = [{"nb"=>"5df54g54df", "active"=>true, "brand"=>"aisle"},{"nb"=>"5jghfj264", "active"=>false, "brand"=>"leg"},{"nb"=>"5qwercv546", "active"=>true, "brand"=>"gem"}]

arr2 = [{"nb"=>"5df54g54df", "active"=>false, "brand"=>"aisle"},{"nb"=>"5jghfj264", "active"=>false, "brand"=>"gem"}]

So far I was thinking something like that :

p (arr1.map(&:nb).find do |nb, val| arr2.map(&:nb)).!Include?(nb && val)

Would you have a suggestion, please?

After finding those who are not present, for those with similar nb.value, how to highlight the difference they have individually? Tks!

CodePudding user response：

My understanding of the question is as follows: "Find the first element h of arr1 (a hash), such that there is no element g of arr2 (a hash) for which h["nb"] == g["nb"] is true".

arr1 = [
  {"nb"=>"5df54g54df", "active"=>true, "brand"=>"aisle"},
  {"nb"=>"5jghfj264", "active"=>false, "brand"=>"leg"},
  {"nb"=>"5qwercv546", "active"=>true, "brand"=>"gem"}
]

arr2 = [
  {"nb"=>"5df54g54df", "active"=>false, "brand"=>"aisle"},
  {"nb"=>"5jghfj264", "active"=>false, "brand"=>"gem"}
]

require 'set'

nbs2 = arr2.each_with_object(Set.new) { |h,st| st << h["nb"] }
  #=> #<Set: {"5df54g54df", "5jghfj264"}>

arr1.find { |h| !nbs2.include?(h["nb"]) }
  #=> {"nb"=>"5df54g54df", "active"=>true, "brand"=>"aisle"}

One could omit the construction of the set nbs2 and compute

arr1.find { |h| !arr2.include?(h["nb"]) }

but that requires a linear search through arr2 for each element h of arr1 that is examined. By contrast, determining whether a set contains a specific element is much faster, with the time required to do so almost independent of the size of the set.

CodePudding user response：

Try this

arr1 = [
  {"nb"=>"5df54g54df", "active"=>true, "brand"=>"aisle"},
  {"nb"=>"5jghfj264", "active"=>false, "brand"=>"leg"},
  {"nb"=>"5qwercv546", "active"=>true, "brand"=>"gem"}
]

arr2 = [
  {"nb"=>"5df54g54df", "active"=>false, "brand"=>"aisle"},
  {"nb"=>"5jghfj264", "active"=>false, "brand"=>"gem"}
]

# Just create a simple lambda for extracting nb values
 
extract_nb = ->(h) { h['nb'] }

# Using map just apply array intersection operation  
# for finding common key of 'nb'

p arr1.map(&extract_nb) & arr2.map(&extract_nb))

optput

["5df54g54df", "5jghfj264"]