Jigsaw Sudoku

Jigsaw Sudoku is a refreshing variation of the regular Sudoku puzzle. Once again, you must fill a square 9x9 grid with digits from 1 to 9, so that no digit repeats in any row or column. The difference from the standard Sudoku is that instead of having non-repeating digits in the 9 3x3 squares in the grid, here you must have non-repeating digits in all the designated irregular regions in grid.

The Jigsaw Sudokus below, sorted by difficulty from 1 to 4, are shared by KrazyDad, a website with thousands of various types puzzle problems.

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