In the sudoku exapmle how can Bob be sure that the three face down cards in a cell are three identcal card?
Without this knowledge, it is easy to pass the final validations without a correct solution.
Each pile has three solutions in it, and you're asking how we know that all three solutions align to the same number, as required by Sudoku.
> Starting with each row, Bob randomly chooses one card in each cell, from the top, the middle, or the bottom
The random assignment of solutions from each pile to each of the three problems means that the only way to consistently pass the test is to have the three solutions in each pile be identical.
> Starting with each row, Bob randomly chooses one card in each cell, from the top, the middle, or the bottom
The random assignment of solutions from each pile to each of the three problems means that the only way to consistently pass the test is to have the three solutions in each pile be identical.