Initial commit

data/sudoku-exchange-puzzle-bank/LICENSE.txt

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+This is a free and unencumbered data set released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or
+distribute this data, either in source form or transformed, for any
+purpose, commercial or non-commercial, and by any means.
+
+In jurisdictions that recognize copyright laws, the author or authors
+of this software dedicate any and all copyright interest in the
+software to the public domain. We make this dedication for the benefit
+of the public at large and to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of
+relinquishment in perpetuity of all present and future rights to this
+software under copyright law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to <https://unlicense.org>

data/sudoku-exchange-puzzle-bank/README.md

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+# Sudoku Exchange "Puzzle Bank"
+
+This repository contains several hundred thousand Sudoku puzzles that were
+computer generated for use by the [Sudoku Exchange](https://sudokuexchange.com/)
+web site.
+
+The puzzles were generated using the
+[QQWing Sudoku](https://github.com/stephenostermiller/qqwing) software, which
+ensure that each puzzle has a unique solution.
+The generated puzzles were then graded using
+[Sukaku Explainer](https://github.com/SudokuMonster/SukakuExplainer) and
+sorted into four 'buckets':
+
+| Filename            | Difficulty Rating |
+| ------------------- | ----------------- |
+| [easy.txt][1]       | < 1.5             |
+| [medium.txt][2]     | < 2.5             |
+| [hard.txt][3]       | < 5.0             |
+| [diabolical.txt][4] | ≥ 5.0             |
+
+Each text file has one puzzle per line, represented as three space-separated
+fields and a Unix-style line-ending, for a total of 100 bytes per record:
+
+     12 bytes of SHA1 hash of the digits string (for randomising order)
+     81 bytes of puzzle digits
+      4 bytes of rating (nn.n)
+      3 bytes of white-space (including the linefeed);
+    100 bytes total
+
+### License
+
+The data set is dedicated to the [public domain](LICENSE.txt).
+
+[1]: https://github.com/grantm/sudoku-exchange-puzzle-bank/raw/master/easy.txt
+[2]: https://github.com/grantm/sudoku-exchange-puzzle-bank/raw/master/medium.txt
+[3]: https://github.com/grantm/sudoku-exchange-puzzle-bank/raw/master/hard.txt
+[4]: https://github.com/grantm/sudoku-exchange-puzzle-bank/raw/master/diabolical.txt

data/sudoku-exchange-puzzle-bank/easy3.txt

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+0000183b305c 451723860007000800000816000000030000005000100730040086906000204840572093000409000  1.2
+0001d5d6314e 302401809001000300000000000040708010780502036000090000200609003900000008800070005  1.2
+000212406270 000823001003000400070000052300960010000102000010038006830000040002000900600789000  1.2