Puzzles and riddles

I have a certain interest in puzzles and riddles. For this reason, it is not strange that it is on of these reoccuring subject in my online diary.

Socks riddle

February 21, 1996: Stated
February 23, 1996: Explained
February 26, 1996: Solution
February 28, 1996: Some more remarks

People standing in a circle

June 28, 1996: Stated and solution
July 1, 1996: Back ground information

Filling the 70x70 square with 1x1 to 23x23

July 11, 1996: Stated and first attempt.
July 14, 1996: My second attempt.
July 17, 1996: The "official" answer.
July 17, 1996: More from Thomas Wolf.

Squares on a grid

September 6, 1996: Description with solution

Goat problem

September 17, 1996: Description with solution
September 9, 1999: Explaination of the solution
December 10, 1999: Solution of an alternative puzzle
July 4, 2002: Intersection of three circles.

Usage Sort

October 30, 1996: Problem described
October 31, 1996: Possible solution
November 4, 1996: Algorithms of others
November 8, 1996: Final algorithm and comparison

Morse reordering puzzle

April 23, 1997: Solution being published

Squares inside squares and rectangles

November 11, 1998: Squares inside squares
March 10, 1999: What Annabel has to say about it
March 18, 1999: Squares inside rectangles
June 9, 1999: The answers

Folding strips of paper

March 11, 1999: Stated

A wooden puzzle

May 14, 1999: Stated

Clickomania

December 28, 2000: Introduced to this puzzle game.
January 10, 2001: Strategies.
January 11, 2001: First program.
January 30, 2003: Game called Collapse.

(proven to be NP-complete for sufficient colors and size.)

Making a CD label

May 29, 2001: Introduced and solved.

Optimization problem

June 1, 2001: Introduced and explained.

Triangle tilings

November 29, 2002: Introduction
December 5, 2002:
December 6, 2002: Hexagon and square grids
February 19, 2003: Wang Tiles
May 12, 2008: Square and triangle tiles

Square tilings

December 6, 2002
February 19, 2003: Wang Tiles
February 19, 2003: Wang Tiles
September 2, 2003: Program
September 3, 2003
August 7, 2007
August 24, 2007: 140 unsolved
August 25, 2007: 132 unsolved
September 16, 2007: 14 unsolved?
September 23, 2007: 10 unsolved?
October 26, 2007: 10 unsolved!
May 12, 2008: Bug found in program
May 13, 2008: Large setback

Havannah

Havannah on MindSports
Havannah on Wikipedia
Formalization
March 9, 2003: Improved formalization
January 5, 2005: Playing
March 21, 2009: Meeting Christian Freeling
July 11, 2011: Monte-Carlo Tree Search
July 13, 2010: The Symple challange
July 17, 2011: MCTS and Symple
July 18, 2011: Fuego
July 23, 2011: Strongest human player
August 3, 2011: Castro, strongest program
August 7, 2011: More Havannah bots
December 29, 2011: Playing and solving Havannah
June 2, 2012: Playing some games
September 14, 2012: Havannah Challenge 2012
October 16, 2012: Christian defeated during challenge
October 19, 2012: Havannah Challenge: 7 - 3

Nonograms

March 8, 2003
December 28, 2003
December 27, 2005: Counter example
December 31, 2005: Smallest 'hard' Nonogram
January 3, 2006: Large nonogram
January 13, 2006
February 14, 2006
February 16, 2006
February 27, 2006
February 28, 2006
March 1, 2006
March 2, 2006
March 3, 2006
March 13, 2006
April 4, 2006
April 5, 2006
April 11, 2006
April 22, 2006: NP-completeness
January 22, 2007: Exact cover
June 13, 2009: Exact Covers of nonograms
June 27, 2009: Exact Covers of nonograms
June 28, 2009: Exact Covers of nonograms
August 18, 2009
August 23, 2009
February 18, 2010: Survery of solvers
August 15, 2010: Knot Nonogram
August 17, 2010: Knot Nonogram (Part 2)
September 8, 2010: Knot Nonogram (Part 3)
January 20, 2011: Polynomial algorithm for 3-Sat
March 7, 2013: Alphabet Cover

Rule 30

September 2, 2003: Square grids
September 3, 2003: Extending "backwards" possible?
November 8, 2003: Extending "backwards" possible!
November 9, 2003: Repeating Rule 30 patterns
January 9, 2005: Repeating Rule 30 patterns
December 18, 2005: Rule 30 jigsaw
December 30, 2006: More Rule 30 Jigsaws
August 7, 2007: Rule 30 square tiling?
August 7, 2007: Mapping cellular automata to tillings

Exact Cover

March 5, 2005: Latin Square algorithm
March 8, 2005: Idea for Exact Cover algorithm
April 24, 2005: Implementation
April 25, 2005: Exact Cover algorithm solves Latin Square
January 13, 2006: Solving the nonogram
January 22, 2007: Nonogram to Exact Cover
January 23, 2007: Solving an Exact Cover
January 27, 2007: Exact Cover Reducer
January 28, 2007: Smallest 'hard' Exact Cover with one solution
February 9, 2007: Smallest 'hard' Exact Cover with one solution
May 12, 2009: Simple, but powerful heuristic
May 17, 2009: Trivial, but powerful heuristic
May 20, 2009: Beat the Computer No. 24
June 13, 2009: Exact Covers of nonograms
June 27, 2009: Exact Covers of nonograms
June 28, 2009: Exact Covers of nonograms
July 19, 2009: Generalization of reduction
July 28, 2009: Exact Cover and ZDD
April 23, 2010: Difficult Exact Cover problems
April 24, 2010: Difficult Exact Cover problems
April 28, 2010: P versus NP
May 24, 2010: XHS paper
May 26, 2010: Single Solution Exact Cover
June 28, 2010: Infinite grid coverings
September 9, 2010: Hardest Sudoku
March 17, 2011: Proof
October 10, 2011: Binary Puzzles
March 7, 2013: Alpabeth Cover

LR-Maze

May 28, 2006: How to escape a maze
June 10, 2006: First algoritm
July 3, 2006: Thinking about it
July 5, 2006: Solution with fixed working set
March 21, 2008: Road Colouring problem solved

Chinese Wooden Puzzle

July 29, 2006: Introduction
September 5, 2006: To the office
November 9, 2006: Small Chinese Wooden Puzzle
December 25, 2006: One six piece solution
December 27, 2006: 3 by 10 solutions
December 28, 2006: 5 by 6 solutions
January 9, 2007: No pieces same colour touching
January 13, 2007: C++ program
January 14, 2007: More solutions
January 16, 2007: Solutions for a hard case
March 11, 2007: Titus finds a solution
November 30, 2007: Error in program?
December 2, 2007: Program seems correct
December 6, 2007: Program is correct
December 8, 2007: Vertical division line
February 21. 2007: 9 by 7 solutions
February 22, 2008: Least connected
October 4, 2009: Compact solutions
October 5, 2009: 15 by 4 solutions
May 22, 2013: Solutions for a hard case

List of solutions

Racing horse game

January 18, 2008: Description
February 1, 2008: Unexpected result

L-tiles

November 18, 2008: Description
November 19, 2008: Correction
November 23, 2008: Swapping L-tiles
November 30, 2008: Swapping L-tiles

Arabic Geometric Patterns

June 11, 2009: Bought the book
June 15, 2009: Reproducing plate 1
June 16, 2009: Reproducing first two plates
June 21, 2009: Reproducing plate 13
August 3, 2009: Reproducing plate 30
Wednesday 23, 2011: book Arabian Geometric Patterns

Latest PostScript file.

P versus NP problem

April 28, 2010: Introduction
May 20, 2010: Boolloop language
May 24, 2010: XHS paper
May 26, 2010: Single Solution Exact Cover
May 27, 2010: Scott Aaronson
June 3, 2010: Informal introduction to the status of the problem
August 9, 2010: NP is not P
September 12, 2010: P versus NP still unresolved
January 20, 2011: Polynomial algorithm for 3-Sat
February 28, 2011: Shortcoming in Sat-3 algorithm
March 17, 2011: Proof
March 30, 2011: Natural Proofs

Infinite grid coverings

June 27, 2010: Introduction
June 28, 2010: Not so infinite

Symple

October 12, 2010: Introduction
October 14, 2010: Defining the Symple Number
October 24, 2010: Symple Numbers for path and square grid graphs
October 31, 2010: Super Symple
November 12, 2010: SyGo
November 19: Complexity of SyGo
December 30: Wintergo
July 13, 2010: The Symple challange
July 17, 2011: MCTS and Symple
February 3, 2012: MCTS program
July 16, 2012: CodeCup 2013

Extremely Loud & Incredibly Close

July 26, 2011: Phone spell
August 4, 2011: Repeating sequences
August 15, 2011: Copy analysis

Jugo Flower

June 11, 2012: Solution to the Jugo Flower
June 12, 2012: More difficult variants
July 1, 2012: Algebra
July 2, 2012: 111101011001000

Diagonal mazes

December 3, 2012: Introduction
December 4, 2012: Labyrinth
March 24, 2013: Computer Science in Vietnam
March 31, 2013: Left/right maze
April 17, 2013: Exact results
April 21, 2013: Colour by length
May 5, 2013: More statistics
May 7, 2013: Percolation theory

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