ruby array custom combinations

Question

What is a good way to get from this:

['a','b','c',['d1','d2']]

to this:

[['a','b','c','d1']['a','b','c','d2']]

another example, from this:

[['a1','a2'],'b',['c1','c2']]

to this:

[['a1','b','c1'],['a1','b','c2'],['a2','b','c1'],['a2','b','c2']]

edit 1:

Sorry for the confusion and thanks for response so far, the individual contents of the array items doesn't matter but the order must be preserved. The method needs to work for both example because the nested array can be in any position of the outer array, and the nested array can have more the 2 elements.

It's sort of like a regex with multiple or conditions

ab(c|d)

expand to match abc and abd

Do you want to combine elements of first array into some random way OR there is some rules that you want to follow? — Darek Nędza
– Darek Nędza, Commented Nov 18, 2013 at 12:12

hirolau · Accepted Answer · 2013-11-18 09:01:36Z

1

It is a bit hard to know exactly what you want, but this produces something quite similar:

# Create a list:
a = [['a1','a2'],'b',['c1','c2']]

# Split it into sub-arrays and single values:
list, other = a.partition{|x|x.is_a? Array}

# Split the array in order to get the product:
list_first, list_rest = list.pop, list

# Get the product  and add the others_values:
p list_first.product(*list_rest).map{|list| list+other}
#=> [["c1", "a1", "b"], ["c1", "a2", "b"], ["c2", "a1", "b"], ["c2", "a2", "b"]]

edited Nov 18, 2013 at 9:01

answered Nov 18, 2013 at 8:55

hirolau

14k9 gold badges39 silver badges51 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

sai Over a year ago

+1 for the partition and product methods usage, it was helpful.

Darek Nędza · Accepted Answer · 2013-11-18 12:41:52Z

1

1st:

arr1 = ['a','b','c',['d1','d2']]
*a, b = arr1
# ["a", "b", "c", ["d1", "d2"]]

a
# ["a", "b", "c"]
b
# ["d1", "d2"]

b.map{|x| a+[x]}
# [["a", "b", "c", "d1"], ["a", "b", "c", "d2"]]

and 2nd:

a, b, c = [["a1", "a2"], "b", ["c1", "c2"] ]

a.product c
#=> [["a1", "c1"], ["a1", "c2"], ["a2", "c1"], ["a2", "c2"]]
a.product(c).map{|x| x<<b}
#=> [["a1", "c1", "b"], ["a1", "c2", "b"], ["a2", "c1", "b"], ["a2", "c2", "b"]]

#or little less readable:
a.product(c).map{|x| [ x[0], b, x[1] ]}
# [["a1", "b", "c1"], ["a1", "b", "c2"], ["a2", "b", "c1"], ["a2", "b", "c2"]]

answered Nov 18, 2013 at 12:41

Darek Nędza

1,4201 gold badge12 silver badges21 bronze badges

1 Comment

toms Over a year ago

nice. a bit shorter version of the 1st: ['a','b','c',['d1','d2']].pop.map{|x| a+[x]}

sai · Accepted Answer · 2013-11-24 12:24:15Z

hirolau got me really close, here is what I ended with so the order is preserved:

# given a sample list
sample = [['a','b'],'c','d',['e','f'],'g',['h','i']]

# partition out the arrays
arrs, non_arrays = sample.partition {|sample| sample.is_a? Array}

# work out all possible products  
first_elem, *the_rest = arrs
products = first_elem.product(*the_rest)

# finally swap it back in to get all valid combinations with order preserved
combinations = []

products.each do |p|
  combinations << sample.map {|elem| elem.is_a?(Array) ? p.shift : elem} 
end

# combinations
=> [["a", "c", "d", "e", "g", "h"],
 ["a", "c", "d", "e", "g", "i"],
 ["a", "c", "d", "f", "g", "h"],
 ["a", "c", "d", "f", "g", "i"],
 ["b", "c", "d", "e", "g", "h"],
 ["b", "c", "d", "e", "g", "i"],
 ["b", "c", "d", "f", "g", "h"],
 ["b", "c", "d", "f", "g", "i"]]

Collectives™ on Stack Overflow

ruby array custom combinations

3 Answers 3

1 Comment

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related