Let's say I have an array like this one:
[
[1, 2, 3, 4],
[3, 4, 5, 6],
[4, 5, 6, 8]
]
I need to get the elements in common between them all. How can I achieve that?
The result should be
common_elements([[1, 2, 3, 4], [3, 4, 5, 6], [4, 5, 6, 8]]) # => [4]
[[1, 2, 3, 4], [3, 4, 5, 6], [4, 5, 6, 8]].reduce(:&) # => [4]
The Array#& method gives you set intersection:
[1, 2, 3] & [2, 3, 4] # => [2, 3]
The Enumerable#reduce method can combine the values in given array using an operation:
[1, 2, 3].reduce(:+) # => 6
Here is another way of doing it "manually lol"... You do each to iterate of over the nested arrays [[0],[1],[2]], then you iterate over each nested array and use include
ary[pos].include?(x) with AND between all three nested arrays to find intersecting value, It will be slow, but handy if you want to add more conditions .
user> ary = [ [1,2,3,4], [3,4,5,6], [4,5,6,8] ]
=> [[1, 2, 3, 4], [3, 4, 5, 6], [4, 5, 6, 8]]
user> ary.each { |f| f.each {|x|
puts "#{x}" if ary[0].include?(x) && ary[1].include?(x) &&
ary[2].include?(x) }}
4
4
4
or simply,
2.1.2 :003 > ary = [ [1,2,3,4], [3,4,5,6], [4,5,6,8] ].inject(:&)
=> [4]
[a=[1,2,3,4], b=[3,4,5,6], c=[4,5,6,8] ]. It's a maintenance nightmare and definitely not recommended or idiomatic.
