Puzzles and riddles

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.

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
• 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

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

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

See also:

• Repeating Rule 30 patterns
• Pseudo-random generator in BF

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

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

• 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