Hackerrank platform.

First question is Amazon Music Pair, easy peasy...
Question #1010

Second question is Item in Container
Not very hard, but not easy to pass all test cases. I only passed half of the cases.
When I wrote my solution approach, I found out we can use 4 arrays to solve it. Two arrays save the left/right "|" index, two arrays save the left/right "|" count. Then time should be O((4+1)*n) = O(n)
But I don't have enough time...