Puzzles that would be nice to add

• SET game puzzles
  • Find all sets
  • Find 20 cards with no set
• Sudoku including this
• Bitcoin mining
• NP-hard problems
  • Traveling salesman (solution uses simulated annealing)
  • https://en.wikipedia.org/wiki/Guillotine_problem (Mathematical Problems category)
  • SAT (in particular, random k-SAT)
• Matrix multiplication
  • Matrix inverse as the solution to matrix multiplication
  • Improvements on a Strassen-like matrix multiplication algorithm
• Compute Huffman codes using Garcia-Wachs algorithm
• Knights tour enumeration using OBDD
• Railroad rush hour, Sokhoban
• Erdos discrepency problem
• Stable marriage
• Stable roommates
• Prouhet–Tarry–Escott problem
• Simple calculus maximizing a 1-d function
• Block stacking problem get creative!
• For the Boolean Pythangorean Triples puzzle we have, can we create a puzzle to address the open problem of Monochromatic Pythagorean Triples problem of coloring the triples with three colors? For example, can you design a puzzle which would prove that it is impossible by finding a subset of triples with a certain property?
• https://en.wikipedia.org/wiki/Disk_covering_problem (Mathematical Problems category)
• https://mathworld.wolfram.com/FiveDisksProblem.html
• https://en.wikipedia.org/wiki/Envy-free_cake-cutting (Mathematical Problems category)
• https://en.wikipedia.org/wiki/Firing_squad_synchronization_problem (Mathematical Problems category)
  • open problem: can you do it with 5 states?
  • See https://www.sciencedirect.com/science/article/pii/0304397587901241 for a 6-state solution
  • This is a hard problem in designing a cellular automaton, could be fun
• https://en.wikipedia.org/wiki/Hadwiger%E2%80%93Nelson_problem (Mathematical Problems category)
  • color the plane so no two unit-distance points have the same color, could be converted to a nice NP problem
• Find longest play in Conway's topswop game