Here’s a new Colombian Sudoku in honor of the number π.
Rules: On the left board, there is a completed Sudoku. On the right board, the dots outside the grid (on the right) indicate how many cells in the corresponding row or column contain the exact same digit as in the same position of the solved Sudoku on the left.
We shall use the chess notation to refer to the numbers at the boards cells.
In the vertical g on the right five digits fit. They can be only the upper 2, the upper 3, 4, 6 and 8. Then g7 is 7 by sudoku.
In the seventh horizontal on the right four digits fit. They can be only one of the 8's, the left 4, the left 6, and 2. So b7 is 4 and c7 is 6.
In the vertical c on the right four digits fit. They can be only the upper 8, 6, 9, and the middle 7. So c8 is 8. Then a7 is not 8 and so i7 is 8.
In the first horizontal on the right four digits fit. They can be only the left 6, one of the 2's, the right 8, and one of the 9's. So a1 is 6 and i3 is not 9.
In the third horizontal on the right two digits fit. They can be only the left 9 and the right 4. So b3 is 9.
In the vertical d on the right five digits fit. They can be only 1, 2, the lower 9, one of the 7's, and 5. So d9 is 1, d6 is 9, and d4 is 5. Then d5 is 8 by sudoku. Thus the lower 7 fits and so d2 is 7. Then by sudoku d1 is 3 and d8 is 4. Moreover, by sudoku f9 is 8.
In the fifth horizontal on the right four digits fit. They can be only 4, one of the 1's, the left 9, and 3. So a5 is 4 and h5 is 3.
In the vertical a on the right two digits fit. They are 4 and 6, so the remaining digits in the vertical a do not fit.
In the ninth horizontal on the right four digits fit. They can be only the right 1, one of the 5's, 2, and 6. So h9 is 6. By sudoku, i9 is 4.
In the vertical i on the right three digits fit. They can be only the upper 8, 2, and the lower 9. So i4 is 2 and i1 is 9. By sudoku, f2 is 9, h8 is 9, and a9 is 9.
By sudoku, c9 is 3. In the ninth horizontal on the right four digits fit. They can be only the right 1, the left 5, 2, and 6. So e9 is 5. By sudoku, b9 is 7, a3 is 7, and h1 is 7. Then g2 or h2 is 5, so b1 is 5.
In the sixth horizontal on the right the only digit which fits is 9. In the vertical b on the right four digits fit. They can be only 4, the lower 1, one of the 3's, and 9. So b5 is 1.
In the vertical h on the right three digits fit. They can be only 6, the lower 3, and the lower 8. So h4 is 8. By sudoku, h6 is 4.
In the fourth horizontal on the right the only digits which fit are 7, the left 5, 8, and 2. So e4 is not 1 and thus by sudoku f4 is 1. >By sudoku, e4 is 4, f1 is 4, and c2 is 4.
In the first horizontal on the right four digits fit. They can be only the left 6, the right 2, 8, and the right 9. So e1 is 2.
By sudoku, c1 is 1, c3 is 2, i3 is 3, h3 is 1, h2 is 2, i2 is 5, e2 is 1, f5 is 2, h7 is 5, a7 is 1, a8 is 5, b8 is 2, a6 is 2, a2 is 8, a4 is 3, b2 is 3, b4 is 6, b6 is 8, i8 is 1, and e6 is 3.
>! In the first horizontal on the right three digits fit. They can be only 8, 7, and the middle 3. So e8 is 7. By sudoku, f8 is 6, f6 is 7, e5 is 6, i5 is 7, and i6 is 6.
Thus the answer is
973158264 9 528476391 8 146293758 7 285937146 6 419862537 5 367541982 4 792685413 3 834719625 2 651324879 1 abcdefghi
