(Note: This app neither produces nor shows how to solve Kakuro puzzles. The intended audience is experienced Kakuro puzzle solvers who need help solving difficult puzzles.)

Many free Kakuro puzzle solving aids merely list all sums that will fit given information. “Filtering out” impossible “combinations” of “digits” from known information about the “clue” is left to the solver. (Refer to “glossary” at end for definitions of “quoted” words.)

Kakuro Combos Pro enables filtering via 3 disjoint (non-intersecting) sets of optional user-supplied digits:
(1) digits that MUST be in the sum (e.g., 7 and 8 are already written down on the puzzle)
(2) digits of which ONE (or more) WILL be in the sum (e.g., 1 or 3 will be in the sum–often easy to know)
(3) digits that CANNOT be in the sum (e.g., 6 will not be in the sum–usually hard to know).
(The combinations shown by Kakuro Combos Free are optionally filtered by ONE digit that MUST be in the sum (option (1)). (At present, it also includes a limited trial of all Pro features.)

A Settings menu can make use of Kakuro Combos Pro more pleasant. Options:
– Always position the cursor at the clue after tapping ‘Show’ (or leave it where it was beforehand).
– Always select the entire field when it gains the focus (or don’t).
– Keep the screen active while the app is running (or let screensaver turn it off).
– Permit landscape mode for tablets (app is designed for portrait).

The following scenario demonstrates the power of option (2). (It also corresponds to screenshots shown elsewhere on this web page.)

Suppose I need to put the clue 30 into 5 cells in a column. There are 6 ways to do so.
Suppose I also know that the sum must contain 7 and 8 (option 1). There are 3 possibilities.
Suppose I also know from an intersecting row that the sum must contain 1 or 3 (option 2).
There is only one possible sum: 1 5 7 8 9.

On the other hand, suppose I need to put the same 30 into 5 cells and I know that the sum must contain 7 and 8, but the only other information I know is that the sum may not contain 6 (option 3).
There are two possible sums. (Option (2) may be the only way to reduce it to one sum.)

This is not to say that option 3 (excluding digits) is useless. But it’s option 3 of 3 for a reason: it’s usually easier to know that one of two digits must be in the sum than to know a digit that cannot.

Notes:
– Minimal error-checking is done. It is assumed that the user knows the rules and will recognize an impossible situation if no results are returned.
– Devices with very small screens may require tapping `Next` multiple times to see all 3 optional input fields.
– This app also could lend itself to helping with Sum-Doku, Jigsaw Sudoku, and other similar puzzles.

Glossary:
digit: one of the numbers 1, 2, 3, … , 9.
clue: the number that must be expressed as a sum of digits to fit into a certain number of cells.
combination: a particular possible sum for a clue.
filtering: the process of eliminating impossible combinations.