Sudoku Solver

To place the numbers/letters so there is only one in each row, column and square group. Built in are 6*6 and 9*9 puzzles, using the numbers 1..6 or 9 and 16*16, using 0..9,A..F.

You can select one of various puzzles and see the occupied squares. ShowAvail allows you to see all numbers which can go in an empty square. Restart reloads the selected puzzle. You can also save the puzzle, perhaps prior to a guess, and later restore it.

If you press BackTrack a solution is sought using backtracking. You are then told if it is solved and in which case how many moves were taken. If you press ShowMoves then you will see all the moves taken. You can slow or speed this.

In backtracking, the puzzle is scanned in order: one of the available numbers is chosen and the next square considered. If no number can go in the next place the current number must be wrong, so the program backtracks and tries a different one.

Alternatively you solve it interactively. Click on a square and you are told which numbers can go there - enter one (or space to remove it). Available numbers are updated.

If you press FindMissing the program will automatically fill in a square if it realises all other numbers are in the same row/column square.

If you press Find One Only the program will determine if only one number can go in a square.

If you press Group Avail the program will update the available numbers if it spots groups.

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