Ruby, get uniq slice from combination
What I have
a = [1,2,3,4]
=> [1, 2, 3, 4]
b = a.combination(2).to_a
=> [[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4]]
b.each_slice(2).to_a
=> [[[1, 开发者_JAVA技巧2], [1, 3]], [[1, 4], [2, 3]], [[2, 4], [3, 4]]]
What I'm trying to achieve is a unique combination
=> [[[1, 2], [3, 4]], [[1, 4], [2, 3]], [[1, 3], [2, 4]]]
I have tried with permutation, flatten, &c. but cannot find the magic ruby code!
Edit :
The answer above is like
b = a.combination(2).to_a
=> [[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4]]
To be more precise.
From
a = [1,2,3,4,5,6]
how to get
=> [[[1, 2], [3, 4], [5, 6]], [[1, 3], [2, 5], [4, 6]], [[1, 4], [2, 6], [3, 5]], [[1, 5], [2, 4], [3, 6]], [[1, 6], [2, 3], [4, 5]]]
which is 5 arrays of uniq values (1,2,3,4,5,6):
[1, 2], [3, 4], [5, 6]
[1, 3], [2, 5], [4, 6]
[1, 4], [2, 6], [3, 5]
[1, 5], [2, 4], [3, 6]
[1, 6], [2, 3], [4, 5]
You seem to have changed the question. Originally you wanted an array of arrays, each of >which had a pair of arrays. Now you want triplets?
Yes, because the first exemple with [1,2,3,4] was too easy, and the answer doesn't fit with a more complex array like [1,2,3,4,5,6] and so one.
this gets you most of the way there i think
[1,2,3,4].combination(2).inject([]){|arr,r| arr << (Hash[*r]); arr}
if you take the first and last element from this array iteratively you get what you were after
def con(h, arr = [])
arr <<[h.delete(h.first).to_a.flatten, h.delete(h.last).to_a.flatten]
con(h, arr) unless h.empty?
p arr
end
#=> [[[1, 2], [3, 4]], [[1, 3], [2, 4]], [[1, 4], [2, 3]]]
Well, it ain't pretty, but it works. combination takes a block.
a = [1,2,3,4]
ans = []
a.combination(2) do |i|
a.combination(2) do |j|
x = [i, j]
y = x.flatten
next if y.uniq != y
ans << x
end
end
puts ans.inspect
EDIT: made it slightly less ugly.
Finally i find a solution without permutation, uniq, combination, flatten :)
a = [1,2,3,4,5,6]
count = a.count
totalloop = count - 1
arrayperloop = count / 2
rounds = []
for round in 0...totalloop
for i in 0...arrayperloop
x = (round + i) % (count - 1)
y = (count - 1 - i + round) % (count - 1)
if i == 0
y = count - 1
end
rounds<<[x + 1, y + 1]
end
end
rounds.each_slice(arrayperloop).to_a give me what i wanted
[[[1, 6], [2, 5], [3, 4]], [[2, 6], [3, 1], [4, 5]], [[3, 6], [4, 2], [5, 1]], [[4, 6], [5, 3], [1, 2]], [[5, 6], [1, 4], [2, 3]]]
Not so ugly ! And always work if we add n*2 integer to the array.
Added this as another answer because it's really a slightly different question - and a lot harder!
def accept(a)
0.upto(a.size-1){|i| return false unless a[i] == a[i].sort
return false if (i > 0 && a[i][0] <= a[i-1][0])}
true
end
x=[1,2,3,4,5,6].permutation.inject([]){|arr, per| arr<< per.in_groups_of(2); arr}
arr = x.inject([]){|arr,y| arr << y if accept(y); arr}
p arr
Not very pretty, but does what you want for any size of array I think
精彩评论