This enables the possibility of a 1 in intersecting square Ei to be excluded. To complete the chain Hd and Hi also form a connected pair. However Ef and Gf form a pair, and Gf and Hd form a pair within the region. A look at the squares where 1s can go, gives a complex and on the face of it is not much help.
#Committed sudoku origin full#
In this case the full force of alternative pair analysis needs to be used to solve another square. This time the twin shared subgroup rules although excluding some possibilities do not allow any more squares to be solved. So often it is not spotting possible usage of a rule that can make you think you have an unsolvable puzzle.Īfter you have solved a few more squares you may well get stuck again. However it is still solvable as there are more complex strategies available that can solve more squares, in this case it is hidden twins and shared subgroups that permit further squares to be allocated. There are no more obvious squares to solve. We have highlighted the squares that differ in the solution. Here is the puzzle and two solutions, both of which fulfill all the rules. Following all the rules you end up with two or more different solutions from the same starting squares.
Multiple Correct SolutionsĪnother example of a puzzle that can not be solved is when it has multiple legitimate solutions. Sudoku Dragon has a hint that will show any incorrect allocations that you have made. Going back and 'Undoing' all the allocations, it turns out that allocating Dd to 8 was the mistake, it should have been a 9. SudokuDragon will spot this incorrect allocation using its hint facility and let you use undo to go all the way back and correct the square allocation. What has happened is that an incorrect choice was made for a square somewhere else and the repercussions of this has shown up here. If you run through the numbers 1 to 9 you will find there is already one of them allocated in a shared row, column or region. In this case there are two squares Bi and Ih that are in a bad state, no numbers can be allocated to these squares at all.
#Committed sudoku origin download#
To download this puzzle and see it in Sudoku Dragon click here.
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