Twin Line-Swapping Sudoku
A pair of Sudoku puzzles that together lead to a complete solution.
Age
14 to 16
Challenge level
Problem
By Henry Kwok
| Twin A | Twin B |
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There is also a downloadable version of the Twin Sudoku.
Rules of Twin Line-swapping Sudoku
This Sudoku variant consists of a pair of linked standard Sudoku puzzles each with some starting digits.
As usual, the object of this Sudoku variant is to fill in the whole of each 9×9 grid with digits 1 through 9 so that each row, each column and each block contain all the digits 1 through 9.
Twin B is related to twin A in the following ways:
Given that twin A is the original puzzle, twin B is obtained by swapping the rows/columns within a chute/band of blocks. By such transformation, twin A and twin B are essentially the same Sudoku puzzle.
For example, figure 2 is obtained from figure 1 below by: swapping row 1 and row 3 within the top horizontal chute/band of blocks, swapping row 5 and row 6 within the middle horizontal chute/band of blocks, swapping row 7 and row 8 within the bottom horizontal chute/band of blocks.
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| figure 1 | figure 2 | figure 3 |
Similarly an equivalent puzzle (figure 3) can be obtained from figure 1 by: swapping column 1 and column 3 within the left vertical chute/band of blocks, swapping column 5 and column 6 within the middle vertical chute/band of blocks, swapping column 7 and column 8 within the right vertical chute/band of blocks.
The three puzzles are equivalent to one another. Equivalent puzzles can also be created from figure 2 and figure 3 by similar transformations.
Student Solutions
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