Exact cover and applications

Stanford Lecture: Don Knuth—&quot;Dancing Links&quot; (2018): <a href="https:&#x2F;&#x2F;youtu.be&#x2F;_cR9zDlvP88" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;_cR9zDlvP88</a>

Interesting exposition about how to use Exact Cover to solve a Sudoku. But in case a sudoku has one solution, it is possible to solve it by reducing the exact cover. For example, if you have a column that is a true subset of another column (with respect to the 1-s) you can remove all the rows that have a 1 in the row with the larger number, because these rows can never be selected.<p>Also when solving an Exact Cover there are some (rather simple) strategies that can improve the speed of finding solutions.<p>I used Exact Covers a lot for solving all kinds of puzzles (most of them far more complicated than Sudoku&#x27;s). See: <a href="https:&#x2F;&#x2F;www.iwriteiam.nl&#x2F;Dpuzzle.html#EC" rel="nofollow">https:&#x2F;&#x2F;www.iwriteiam.nl&#x2F;Dpuzzle.html#EC</a> for a list of blogs I wrote over the time.

I must be missing something. malib does not have solve_cover, and this specific function is used without definition in the Sudoku example. The shown solution seems to be the order in which the digits are solved and not the actual digits in their correct location, because the solution matrix has repeat digits everywhere, and the first 21 digits are the provided solution digits in order.