Now download the jigsaw sudoku puzzle magazine and enjoy 100 fun jigsaw sudoku puzzles. We can eliminate 4,8 as candidates from all other cells in row four this now means that the 8 can be placed in row five, in turn enabling us to place precisely the 4 and 8 in row four. This enables us to say that R4C5 and R4C6 must be 4 and 8, so we can mark 48,48 as the pencilmarks in those cells. With the 1 in column 5 and the 3 in column 6, this makes the candidates for those cells respectively: 137, 37, 17. This will just leave 1,3,7 which must be placed in cells 4,5,6 in row 6 accordingly. The 5 in row six can also be placed instantly. We can instantly place the '6' in row six using the simple logic above, and it pays dividends taking the time at the start of the puzzle to look for numbers that must go in a particular cell in a row, column or box. You will tend to find that you need to use pencilmarks a lot more with jigsaw sudoku than you do with normal sudoku (unless you are doing a particularly hard sudoku that relies on you going through and noting down each candidate for a particular cell systematically to reduce the options). Looking out at the start of the puzzle for applications of this can be the key to placing values quickly in jigsaw sudoku and making the appropriate eliminations as a result. This only leaves one cell that can contain the 1 in row 1, and that is the final cell, R1C9, and we place it there. This only leaves three cells in row 1 that can contain a 1, but in fact cells 1,2 can't either because there is a 1 placed in R2C2 which contains cells R1C1 and R1C2 in its boundaries. We can see that the '1' in cell Row three Column 5 (R3C5) means that cells 3,4,5,6,7,8 in row one cannot contain a 1. Those that spread across a particularly large number of cells in another region (intersect over those cells) are particularly useful. The key to solving jigsaw sudoku is of course to make the most of the shapes of the regions. However, there is one rule that you will find yourself using a lot more than in normal sudoku and that is region intersection elimination. The rules that you use in standard sudoku certainly apply, that there is 1 - 9 once in each row, column and in this case irregular shaped thick lined set of nine cells. One of the most enjoyable elements about it is that there are many possible grid types, and therefore each of these presents a different set of regions and therefore a different puzzle each time. This puzzle is one of the more common and more fun of the various sudoku variants. My own personal experience is that it is not common to find that you need this technique to solve a puzzle.Our Irregular sudoku puzzle magazine, also referred to as Jigsaw Sudoku, has 100 all new irregular sudoku puzzles for you to enjoy. Net result: any "5" along a red line that's not in a blue line can be removed (all the 5s in the pink cells can be erased).Īpparently, some examples of this technique create a pattern that resembles the actual fish it's named after. We don't know which blue line we just know it's at a blue line. The result is each red line's 5 is going to be where a blue line crosses it. Why is this important? Well, it isn't - unless the red lines have other 5s in them somewhere! You see, each of the three blue rows is going to have a 5, and since the possible locations are limited, each row will end up having a 5 in one of the red lines. Let me say that a different way: The blue lines only have 5s where the red lines cross. Here is the same puzzle, but with some markings added for illustration:Īs you can see, the three rows marked by the blue lines all have their possible locations for a 5 confined to the same three columns (marked by the red lines). There are three rows where all the possible 5s appear in the same three columns. The puzzle above has a Swordfish on the number 5. It is not super complex to understand - it's just very hard to spot one.īut, in the interest of being complete, I will cover it. I must confess - this is probably my least favorite technique. Even if you know it's there, it can take some time to find. Just as the X-Wing involves two candidates in two columns or rows, the Swordfish involves three candidates in three columns or rows.
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