Kakuro Solver
Solve a Kakuro (cross-sums) puzzle from its run clues.
Kakuro, also called cross-sums, is a number crossword. White cells take a digit from 1 to 9, and every straight run of white cells must use different digits that add up to the run's clue. Clues live in the block cells: the arrow-right total is the run heading right, the arrow-down total is the run heading down. Click a cell to switch it between white and block, type the clue totals, then solve.
Click a cell to switch white or block. In a block, → is the across total and ↓ is the down total.
How it works
Each clue starts a run of white cells, going right or down, that must use different digits adding to the clue. The solver fills the white cells one at a time, and after each digit it checks every run the cell belongs to: the digit must be new to that run, and the digits left to place must still be able to reach the run's total. Those bounds cut the search down quickly.
A well-formed Kakuro has one solution; the solver reports when more than one set of digits fits.