min-max-product

List the product of the minimum and maximum integers during the execution of a list of commands.

Motivation

I developed this small application for an assessment applying for a job.

I publish it for later reference for anyone for anything that might be needed.

Description of the problem

The input data will be given as pairs of command and value. Valid commands are "push" and "pop" and the value is always integer. These operations are executed on a set of integers where the given value is stored and removed.

Each time any operation is executed, the minimum and the maximum must be calculated and the product of these two must be stored as part of the solution.

Two examples are given:

In the first example, we have the sequence

push 1
push 2
push 3
pop 1

that must output

1
2
3
6

The execution is like

push 1 -> set = {1}; min = 1; max = 1; product = 1
push 2 -> set = {1,2}; min = 1; max = 2; product = 2
push 3 -> set = {1,2,3}; min = 1; max = 3; product = 3
pop  1 -> set = {2,3}; min = 2; max = 3; product = 6

In the second example, we have the sequence

push 3
push 2

that must output

9
6

The execution trace is

push 3 -> set = {3}; min = 3; max = 3; product = 9
push 2 -> set = {2,3}; min = 2; max = 3; product = 6

Compilation and execution

It is made for Java 5 and above, and I didn't use any project management builder like Maven for it, so that, you will need to use the "old school style" to compile it:

javac -d . Solution.java

and execute it with:

java -cp . Solution

if everything went fine, it shall print

1
2
3
6
===
9
6

About the development

The class "Dataset" handles the intermediate state and the solution. The attribute "elements" keeps track on the elements already sorted, and the attribute "products" the partial solution.

Actually, the minimum value is given by the "first" method of "elements", and the maximum value is given by the "last" method of "elements", so that, no need to keep the cache with the attributes "min" and "max".