7
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This is subtraction sudoku.

The rules are basically the same as common Sudoku, but with a few additions.

In the row, the number in the orange box is the difference when its left side (sum of 3 squares) is subtracted from its right side (sum of 3 squares). Similarly, for columns, the number in the box is the difference between its top side and its bottom side.

Check the samples below!
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There is only 1 unique solution! Find it!

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  • $\begingroup$ Do we need to get all the numbers 1-9 in each of 3 X 3 squares and that too only once and also row-wise, column-wise as well? $\endgroup$ – Mea Culpa Nay Nov 17 '17 at 11:04
  • $\begingroup$ Yes, like common sudoku I said. $\endgroup$ – Jamal Senjaya Nov 17 '17 at 11:47
5
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The solved sudoku:

Solve path:

For each row and each column we have 3 formulas, the two given differences and $45$ as the sum. With that we have all the sums of the rows and columns in each 3x3 square. Starting with the rows that have a sum of $7=1+2+4$ and the only number that is already filled, we can slowly but surely solve square by square.

Row sums: $\begin{array}{r|r|r} 15 & 11 & 19 \\ \hline 7 & 20 & 18 \\ \hline 23 & 14 & 8 \\ \hline 13 & 8 & 24 \\ \hline 18 & 20 & 7 \\ \hline 14 & 17 & 14 \\ \hline 20 & 11 & 14 \\ \hline 18 & 12 & 15 \\ \hline 7 & 22 & 16 \end{array}$ Column sums: $\begin{array}{r|r|r|r|r|r|r|r|r} 10 & 18 & 17 & 10 & 21 & 14 & 17 & 12 & 16 \\ \hline 18 & 17 & 10 & 19 & 8 & 18 & 17 & 15 & 13 \\ \hline 17 & 10 & 18 & 16 & 16 & 13 & 11 & 18 & 16 \end{array}$

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  • $\begingroup$ Wow, I thought this puzzle will take more time to solve. +1 for speed. $\endgroup$ – Jamal Senjaya Nov 17 '17 at 11:55
  • $\begingroup$ @JamalSenjaya I was lucky and saw this puzzle shortly after it was posted and had some time to kill. There also was a nice solve path to follow instead of lots of guessing. $\endgroup$ – w l Nov 17 '17 at 12:15

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