Off-campus: technical round with 2 hashmap/frequency-tracking problems, then HR, resulted in an offer

I had my 1st round yesterday.
It had 2 Questions:

1. Find the string with highest frequency from a given array of strings.
   Eg. ["hello", "world", "world", "bar", "hello", "hello"] should output "hello" (frequency = 3).

2. Design data-structure(s) to implement these functions in most efficient way:
   Class Solution {
   void incr(String s) {} //increment frequency of a string
   void decr(String s) {} //decrement frequency of a string
   String getMax() {} //return string with maximum frequency
   String getMin() {} //return string with minimum frequency
   }

Eg.
incr("hello")
getMax() -> "hello"
incr("world")
incr("world")
getMax() -> "world"
decr("hello")
getMin() -> "world"

UPDATE:

Had 2nd round of HR interview .

Result: Got The Offer