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Recent content in Home on Damien ZhangHugo -- gohugo.ioen-usSun, 11 Feb 2018 17:23:18 -0500Solving Sudoku Using Preemptive Sets
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Sun, 11 Feb 2018 17:23:18 -0500http://damienzhang.com/sudoku/A while back, the American Mathematical Society published a paper by J. F. Crook titled “A Pencil-and-Paper Algorithm for Solving Sudoku Puzzles” that claimed to provide a way to solve any Sudoku puzzle using only paper and pencil.
This is less impressive than it sounds, though, because people were already solving Sudoku puzzles just fine. It’s just that the hard ones would often require the uncomfortable step of taking a blind guess to make further progress.Countdown to 2018
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Mon, 01 Jan 2018 00:00:00 +0000http://damienzhang.com/countdown-to-2018/Here’s a fun puzzle for the new year from Alex Bellos:
Fill in the blanks so that this equation makes arithmetical sense: $$10\ 9\ 8\ 7\ 6\ 5\ 4\ 3\ 2\ 1 = 2018$$ You are allowed to use only the four basic arithmetical operations: $+$, $-$, $\times$, $\div$. But brackets can be used wherever needed.
So how do we approach this problem? The instructions tell us that we can use brackets whenever we need, so we are not merely choosing which operator goes between each pair of number.About
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