Sandwich Sudoku Explained in One Short Example
A row with a clue of 10 shows the sandwich rule. Two cells sit between the 1 and the 9, and 3 + 7 = 10 matches the clue.
Transcript
The rule
In sandwich sudoku, numbers outside the grid give a clue for each row or column. The clue is the sum of the digits sandwiched between the 1 and the 9 in that line.
The clue tells you how far apart the 1 and the 9 can be. Small clues keep them close together, and big clues push them toward the ends.
Worth memorizing
0 means the 1 and 9 are next to each other.
35 means the 1 and 9 are at the two ends, since 2 + 3 + … + 8 = 35.
Small clues mean few cells between: 2 or 5 is too small for three digits.
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