Sandwiches by the Seaside

This is part 31 of the puzzle series Around the World in Many Days. Each part is solvable on its own.

Dear Puzzling,

This is a sandwich sudoku puzzle. Each of the eight different letters in the grid represent a different digit between 1–8. A few digits have been given as is, without the letter conversion. These have been marked in blue for convenience. Fill the grid so that every row, column and 2x4 box contains the numbers 1–8 exactly once. Numbers outside the grid indicate the sum of digits sandwiched between the 1 and the 8 in that row or column. For example, if a row consists of the numbers 51438276, the sandwich sum for that row would be 7 because the sum of the numbers between the 1 and the 8 is 4+3=7. The grey arrows with numbers are not part of the sudoku; they are simply there to help you find the final answer in the end.

Today I have sunbathed by the seaside right next to an international airport, watching passenger planes go by. Can you guess where I am?

Gladys will return in Where’s the Puzzle?

First, note that 1 is an impossible sandwich sum, and every letter except B appears as a sandwich sum.
So B=1

That immediately places the sandwiches in rows four and eight, and columns six and seven, and tells us C=4 and U=8.
And that places the sandwich in row seven as well.

(I've used the solid black circle numbers because I found numbers over letters hard to read.)

In column eight, the 8 must be in the first box (row 1 or 2), but M != 8, so must be in R1C8.
That places the 1 the other side of the M.
And that places the sandwich in row three.

In column four, m is at most 7, so the sandwich contains at most two digits of filling.
So the 1 must be in R6C4.

In column three, the 1 can only go in R2C3, and the sandwich sum tells us M=6.
In column five, the 1 can only go in R5C5.

In row five, the 1 is not adjacent to the 6, so sandwich sum must be 4+2, giving us H=2.

The final 8 goes in R2C1, giving us O=3 from the sandwich sum in column one.

And from there, basic sudoku deuctions get us to:

In row 6, the sandwich sum gives us E=7, and by elimination A=5.
And from here, more basic sudoku deduction complete the grid:

Finally:
Following the directions from the 6 and the 1, we get the digits 6523 17542, which when converted back to letters give us Maho Beach.

• Nice work! That black-circle notation is so much clearer than how I would have presented it (letters with little numbers in the corner). Definitely stealing that.
– Jafe
Jul 19, 2023 at 10:47
• @Jafe Thanks. It does mean you can't see the letters any more though.
– fljx
Jul 19, 2023 at 11:29