Compare ruby array of arrays

Question

I have this array

a = [[1,2,3,4,5],[2,3,6],[2,8,9]]

How can I get the intersection of all the arrays in a ? It should be the same as a[0]&a[1]&a[2] , which is:

[2]

Answer 1

a = [[1 ,2, 3, 4, 5], [2, 3, 6], [2, 8, 9]]

a.inject(:&)
# => [2]