My AlgoUniversity interview experience and assistance

It's my very first interview with the algo university team after clearing all the before rounds namely bootcamp on graph,  followed by evaluation test then after  one technical assessment. Finally the interview. It's a mixture of sections including operating systems, OOPS concepts in Java programming language,and followed by one problem solving question.  And the question is to find the highest occurance of an character in the given string. It's little difficult to me as I am not good enough in ...