A cool algorithm to check a Sudoku field?

Question

Does anyone know a simple algorithm to check if a Sudoku-Configuration is valid? The simplest algorithm I came up with is (for a board of size n) in Pseudocode

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Answer 1

Just a thought: don't you need to also check the numbers in each 3x3 square?

I'm trying to figure out if it is possible to have the rows and columns conditions satisfied without having a correct sudoku