Can we use data structures other than Hash Map to implement Random search of client info in Multiplexing Server. What will be the Amortized cost?

I would use a Red-Black tree to map keys to values. It maintains the keys in sorted order so it is good for

taking the value from a given index

inserting a value at a given index

deleting a value at a given index

You have to be a little bit more specific in your question about data mining.

There are several data mining tasks, including classification, regression, clustering, dependence modeling and others.

data mining algorithm can solve each of these tasks separately. Therefore, the first step in designing a data mining algorithm is to define which task the algorithm will address

Hope I helped