I have a challenge, im trying to write a method that takes in an array and returns the subset and permutation of twos, including the initial array. How do I check for particular patterns in the array. For example, given this array:
[a,b,c]
subset return will be:
[a,b,c,], [a,b], [b,c], [c,a]
and I also need to check if each subset contains a particular letter. Here's my code:
def conflict_free?(a)
return a.permutation(2).to_a
end
Here's how to get the subsets you're looking for:
def subsets(a)
2.upto(a.length).flat_map {|n| a.combination(n).to_a}
end
irb(main):023:0> subsets(["a", "b", "c"])
=> [["a", "b"], ["a", "c"], ["b", "c"], ["a", "b", "c"]]
Anything else you want, you'll have to edit your question and provide more detail.
2.upto(a.length).flat_map {|n| a.combination(n).to_a}
2.upto(a.length-1).flat_map {|n| a.combination(n).to_a}<<a or [a] + 2.upto(a.length-1).flat_map {|n| a.combination(n).to_a}a.combination(3).to_a.Here is a very compact and fast solution :
def conflict(a)
a.combination(2).to_a << a
end
>> [["a", "b"], ["a", "c"], ["b", "c"], ["a", "b", "c"]]
If you did want the initial array at the beginning you sacrificing a fair bit of speed. Nevertheless the best way to do it :
def conflict(a)
temp = [a]
a.combination(2).each { |com| temp << com}
temp
end
>> [["a", "b", "c"], ["a", "b"], ["a", "c"], ["b", "c"]]
If the input is not 3 then this will work :
def conflict(a)
temp = []
2.upto(a.size-1) {|i| temp += a.combination(i).to_a}
temp << a
end
The initial array can be added at the beginning or end. Above it's at the end.
def conflict_free?(a) return a.permutation(2).to_a end[a,b], etcbut also[b,a], etcin your example you don't have the switched permutations, did you still want those ?