Was asked this in a phone screen. How do you find the intersection of k sorted arrays. I think interviewer was expecting a heap answer ( similar to union of k sorted arrays using iterators given in EPI ) but I can't really tell if heap is possible or if he was expecting something else. I couldn't solve it. What is the best way to solve this without running a loop around each array.

INPUT: [[1,3,5,7], [1,1,3,5,7],[1,4,7,9], [1,7],[1,2,3,7]]
OUTPUT: [1,7]