Ruby - What exactly "combination" does?

Question

c = [1,2,3,4].combination(4)
puts c.to_a

Answer 1

Paolo De Nictolis
Have you ever heard about permutation and combination in mathematics. Same that combination is used here which create combination of defined side as you have defines 4 as size here and all 4 elements can make one combination so for understanding the concept try to create combination of size 2 or 3 like this way.

a = [1, 2, 3, 4]
puts "combination a : #{a.combination(2).to_a}\n\n"

b = [1, 2, 3, 4]
puts "combination b : #{b. combination(3).to_a}\n\n"

c = [1,2,3,4].combination(4)
puts c.to_a

d = [1, 2, 3, 4].combination(3)
puts d.to_a

https://code.sololearn.com/c2y8wS8w559K/?ref=app

Answer 2

Paolo De Nictolis what you are assuming is permutations not combination. Here is an example of permutations which are 24 for 4 length list. Which is factorial (n!) Where n is the length or size of list

https://code.sololearn.com/cbCY86XcFJ7C/?ref=app

Answer 3

Just about I heard about.... There are 24 combinations of four elements!