First sort specific array elements

Question

I have a ruby ​​array that looks something like this:

my_array = ['mushroom', 'beef', 'fish', 'chicken', 'tofu', 'lamb'] 

I want to sort the array so that "chicken" and "beef" are the first two elements, then the rest of the elements are sorted alphabetically. How can i do this?

Answer 1

 irb> my_array.sort_by { |e| [ e == 'chicken' ? 0 : e == 'beef' ? 1 : 2, e ] } #=> ["chicken", "beef", "fish", "lamb", "mushroom", "tofu"] 

This will create a sort key for each element of the array, and then sort the array elements by their sort keys. Since the sort key is an array, it is compared by position, so [0, 'chicken'] < [1, 'beef'] < [2, 'apple' ] < [2, 'banana'] .

If you don’t know which elements you wanted to sort to the front before execution, you can still use this trick:

  irb> promotables = [ 'chicken', 'beef' ] #=> [ 'chicken', 'beef' ] irb> my_array.sort_by { |e| [ promotables.index(e) || promotables.size, e ] } #=> ["chicken", "beef", "fish", "lamb", "mushroom", "tofu"] irb> promotables = [ 'tofu', 'mushroom' ] #=> [ 'tofu', 'mushroom' ] irb> my_array.sort_by { |e| [ promotables.index(e) || promotables.size, e ] } #=> [ "tofu", "mushroom", "beef", "chicken", "fish", "lamb"] 

Answer 2

Mine is much more general and more useful if you only get your data at runtime.

 my_array = ['mushroom', 'beef', 'fish', 'chicken', 'tofu', 'lamb'] starters = ['chicken', 'beef'] starters + (my_array.sort - starters) # => ["chicken", "beef" "fish", "lamb", "mushroom", "tofu"] 

Answer 3

Another way to solve this problem:

 array = [1,2,2,3,3,4,5] array.select {|element| element == 2} + array.select {|element| element != 2} # => [2, 2, 1, 3, 3, 4, 5] 

Answer 4

Can just do

 firsts = ["chicken", "beef"] [*firsts, *(my_array.sort - firsts)] #=> ["chicken", "beef", "fish", "lamb", "mushroom", "tofu"]