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Borderland Sudoku (Round 3 Puzzle 15)

published by Yolandria on Wed, 03/11/2026 - 18:15
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General discussion

Hi,

I don't understand how I construct the additional Boxes from the information given. Am I missing sonething, as in the solution many boxes don't have any defining number for the size? Must the block end when encountering a number of different parity, or are the borders unrelated to that?

Thanks for any pointers

Submitted by Mike on Thu, 03/12/2026 - 05:18.

1. Not all digits equal to the size of the block it is in are marked, and there can be blocks without any marked cells.
2. The block must end when encountering a number of different parity. The borders in the solution are for clarity.

Deep Shikha Sanghi's picture

Submitted by Deep Shikha Sanghi on Thu, 03/12/2026 - 10:03.

Can you explain Borderland sudoku in detail.

Submitted by Mike on Thu, 03/12/2026 - 12:53.

Look at the cells R2C3,R3C3,R3C4,R4C4,R4C5,R5C4,R5C5 in the example solution. They are orthogonally connected and all contain odd numbers, and all other cells adjacent to one of these cells contain even numbers. This is called a "block".
Sometimes there is one or more marked cells in a block. In this case, the number in each marked cell must equal the size of the block it is in. For example, the marked cell R4C4 contains the number 7, which is exactly the size of the block it is in (the block shown above).