halcyon / exercises

Design considerations for Exercises 1 and 2

In a production product, I would invest additional effort into developing either a tail-call optimized approach or an iterative solution. A tree of sufficient depth could overflow the stack in my current implementation. While the JVM does not currently provide support for TCO at the bytecode level, there is a technique to add TCO when using streams as described by Venkat Subramaniam in Functional Programming in Java: Harnessing the Power Of Java 8 Lambda Expressions. Another alternative would be to utilize an iterative approach. This would involve the maintenance of a stack structure as the graph is walked.

I considered declaring walkGraph and paths as static methods. In a real world project I would surface this for consideration by the team.

Proposed Amendments

I captured a few minor items that cought my attention in the requirements document. My apologies in advance if I’ve misinterpreted the intent of any of these. Even the best of requirements can have gaps. The ability to identify and fill these gaps can be a valuable skill. In a real world project such concerns would be surfaced to the appropriate stakeholders.

Proposed amendments to SWE Java Challenge.docx (original -> proposed)

• Line #24 public ArrayList walkGraph(GNode); -> public ArrayList walkGraph(GNode node);
• Line #33 public ArrayList paths(GNode node); -> public ArrayList<ArrayList<GNode>> paths(GNode node);

Exercises 1 & 2

Environment

• Java: openjdk-10.0.2
• Gradle: 4.10

How to run

From within the exercises-1-and-2 directory run:

gradle run

Expected Output

> Task :compileJava UP-TO-DATE
> Task :processResources NO-SOURCE
> Task :classes UP-TO-DATE
> Task :run
[A, B, E, F, C, G, H, I, D, J]
[[A, B, E], [A, B, F], [A, C, G], [A, C, H], [A, C, I], [A, D, J]]
BUILD SUCCESSFUL in 0s

How to test

From within the exercises-1-and-2 directory run:

gradle test

Expected Output

> Task :compileJava UP-TO-DATE
> Task :processResources NO-SOURCE
> Task :classes UP-TO-DATE
> Task :compileTestJava UP-TO-DATE
> Task :processTestResources NO-SOURCE
> Task :testClasses UP-TO-DATE
> Task :test
AppTest > testZeroLevelsDeep PASSED
AppTest > testOneLevelDeep PASSED
AppTest > testTwoLevelsDeep PASSED
AppTest > testCanonicalExampleData PASSED
AppTest > testFourLevelsDeep PASSED
BUILD SUCCESSFUL in 1s

Exercise 3

Environment

• Java: openjdk-10.0.2
• Clojure: 1.9.0
• Requires installation of “Command Line Tools” available at Getting Started
  • Optionally if using mac or linux, one can use the ASDF Version Manager to install the Clojure Command Line Tools using the ASDF Clojure plugin

How to run

From within the exercise-3 directory run:

clj -m com.zeddworks.exercise-3 README.md

Expected Output

{"Files" 1,
 "obtained" 1,
 "compare" 1,
 "provide" 1,
 "org" 1,
 "3" 4,
 "zeddworks" 2,
 "Run" 2,
 "s" 1,
 "Changed" 1,
 "md" 1,
...

How to test

From within the exercise-3 directory run:

clj -A:test:runner

Expected Output

Running tests in #{"test"}
Testing com.zeddworks.exercise-3-test
Ran 1 tests containing 1 assertions.
0 failures, 0 errors.