Practices

A small scratch collection of competitive-programming and recursion practice — mostly Ruby, with a couple of ported variants.

Contents

A handful of solutions and experiments from Aizu Online Judge (AOJ) and paiza, plus some self-study scripts.

aoj/ — Aizu Online Judge

File	Demonstrates
ITP1_1_B.rb	The classic "cube of an integer" warm-up — reading input and printing n**3.
vol2000.rb	A grid simulation: moving a set of points by N/S/E/W directions and removing any that reach a target cell.

paiza/ — paiza problems & experiments

File	Demonstrates
D005.rb	Reopening Integer with a repeat method built on Enumerator to lazily generate an arithmetic sequence.
D009.rb	Trivial difference of two whitespace-separated integers.
Hanoi.rb	Recursive Tower of Hanoi that prints every move (depends on starter.rb).
Hanoi2.rb	A variant that only prints the board at a specified step number.
hanoi.js	The same Hanoi solver ported to JavaScript.
hanoi.lisp	The same Hanoi solver ported to Common Lisp.
integer.rb	Monkey-patching Integer#! to compute factorial (5.!).
Mod7.rb	A combinatorics count: triples whose sum is divisible by 7, using bucket counts and factorial deduplication.
my_script.rb	A one-line curiosity — a script that re-invokes itself with system.
POH6plus.rb	String puzzle building a palindrome from reversible-pair words.
recursion.rb	A minimal recursive factorial that prints each step.
starter.rb	Shared helpers: a Range#each patched to count downward, String#to_ia for parsing int arrays, and gets_ia.

Usage

Each script reads from standard input and prints to standard output, matching the judge it was written for.

# Ruby
ruby aoj/ITP1_1_B.rb        # then type input, e.g. 3
echo 3 | ruby aoj/ITP1_1_B.rb

# The Hanoi scripts require starter.rb (already require'd via a relative path)
echo 3 | ruby paiza/Hanoi.rb

# JavaScript variant (the original used a Rhino-style print(); adapt as needed)
node paiza/hanoi.js

# Common Lisp variant (e.g. with SBCL)
sbcl --script paiza/hanoi.lisp 3

Project layout

.
├── aoj/
│   ├── ITP1_1_B.rb
│   └── vol2000.rb
└── paiza/
    ├── D005.rb
    ├── D009.rb
    ├── Hanoi.rb
    ├── Hanoi2.rb
    ├── hanoi.js
    ├── hanoi.lisp
    ├── integer.rb
    ├── Mod7.rb
    ├── my_script.rb
    ├── POH6plus.rb
    ├── recursion.rb
    └── starter.rb

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