Solutions to the problems :
Question 1 - MinimumUniqueArraySum.java
Question 2 - StackDriver.java - This file has multiple classes. One for Driving the program and others for stack implementation using both linked list(custom written) and arraylist. However, running the file would remain the same and would implement linked list by default.
Question 3 - CountingPairs.java
The input and output is as per the sample i/o in the pdf document. Importing these files in Eclipse also should work