Software Engineering

Unknown Language Coding Problem

Bruce Ediger

This is from the Daily Coding Problem email list. The owners of that list haven’t sent out a problem that caught my imagination in quite a while.

Daily Coding Problem: Problem #1553 [Hard]

This problem was asked by Airbnb.

You come across a dictionary of sorted words in a language you’ve never seen before. Write a program that returns the correct order of letters in this language.

For example, given ['xww', 'wxyz', 'wxyw', 'ywx', 'ywz'], you should return ['x', 'z', 'w', 'y'].

Github repo for my solution. Feel free to look it over, try it and email me ( if you notice anything.

Gall's Law

Bruce Ediger

I ran across an engineering aphorism or principle called “Gall’s Law”:

A complex system that works is invariably found to have evolved from a simple system that worked. The inverse proposition also appears to be true: A complex system designed from scratch never works and cannot be made to work. You have to start over, beginning with a working simple system.

GPP Quine

GPP Quine

Bruce Ediger

GPP is the General Purpose Preprocessor, a macro preprocessor for various forms of structured and unstructured text.

A quine is a computer program which takes no input and produces a copy of its own source code as its only output. There’s usually a few conditions on what the program can do, like not reading it’s source code during execution.

I wrote what I believe to be the first non-vacuous quine ever in the GPP language.

Daily Coding Problem

Bruce Ediger

There’s at least two things that one might conflate under the “Daily Coding Problem” rubric:

They’re related, as the book is a byproduct of the success of the email list. Both are deficient, but for different reasons

Self Relocating Program

Bruce Ediger

Once upon a time, I wrote a reasonably-strict-C89 C language program that “relocates” a function in memory and then runs it. That relocated function can relocate itself again, and run that copy, and so on and so forth.

Github repo for this program