Preferably in Ruby
I need a way to determine if one array is a "subarray" of another array when order matters
For instance,
a = ["1", "4", "5", "7", "10"]
b = ["1", "4", "5"]
c = ["1", "5", "4"]
d = ["1", "5", "10"]
a includes b = true
a includes c = false
a include d = false
Thanks in advance.
[b, c, d].map do |arr|
a.each_cons(arr.length).any?(&arr.method(:==))
end
#⇒ [true, false, false]
This is definitely not the most performant solution, but for not huge arrays is works and, which is important, is readable.
a.each_cons(arr.length).include?(arr) to achieve same effect?a = ["1", "4", "5", "7", "10"]
b = ["1", "4", "5"]
c = ["1", "5", "4"]
d = ["1", "5", "10"]
def sub_set?(arr_a, arr_b)
arr_a.select.with_index do |a, index|
arr_b[index] == a
end == arr_b
end
puts "testing sub_set #{a.inspect} and #{c.inspect}"
puts sub_set?(a,c).inspect
detect.with_index { |a, i| arr_b[i] != a } instead of select to fail fast.detect {...} ? false : true.
class Array
def includes(array)
return false if array.size > self.size
indexes = []
self.each_with_index {|e, i| indexes << i if e == array[0]}
p indexes
indexes.each do |i|
return true if self[i..i+array.size-1] == array
end
return false
end
end
p a.includes b
p a.includes c
p a.includes d
Or less phpish :)
class Array
def includes(array)
return false if array.size > self.size
indexes = each.with_index.select { |e, i| e == array[0] }.map(&:last)
indexes.each {|i| self[i..i+array.size-1] == array ? (return true) : (return false)}
end
end
p a.includes b
p a.includes c
p a.includes d
indexes = select.with_index { |e, i| e == array[0] }.map(&:last) would be less phpish.indexes = each.with_index.select { |e, i| e == array[0] }.map(&:last), because if select goes before with_index, it selects plain elements.You could join the elements with an arbitrary character then compare strings:
a.join(' ').match?(array.join(' '))
This works for the test cases you have provided:
a.join(' ').match?(b.join(' '))
#=> true
a.join(' ').match?(c.join(' '))
#=> false
a.join(' ').match?(d.join(' '))
#=> false
But this is not a general solution and will fail on varying types of arrays (see comments for further discussion).
