Solving Process#

When working with the Custom Solver or when making use of the API, your interaction with the package goes beyond the simplified functional access and you will be confronted with the objects that, e.g., represent the solving algorithms or the rendering frontend. In order to understand how these objects interact with each other, a basic understanding of the solving procedure, illustrated by the flowchart below, is indispensible.

We come back to some specific nodes of the diagram when discussing the API or the Custom Solver generator.

Flowchart#

flowchart
    init([Launch Solver]) --> InitialAlgorithm[Use initial Algorithm]
    InitialAlgorithm --> LaunchSolver[Launch Algorithm] 
    LaunchSolver --> Solved{Puzzle \nsolved?}

    Solved --Yes--> Return([Return Solved Puzzle])

    Solved --No---> SolverLoop[Loop over Tiles]
    SolverLoop --> Increase[Next Tile]
    Increase --> TerminateLoop{Last \nitem?}

    TerminateLoop --Yes--> CheckSuccess{Algorithm \ncould remove \nat least one\n candidate?}

    CheckSuccess --No---> FallbackLeft{Fallback \nAlgorithm \nspecified?}
    FallbackLeft --Yes--> Fallback[Continue with Fallback Algorithm]

    CheckSuccess --Yes--> Advance[Continue with less elaborate Algorithm]
    Fallback & Advance --> LaunchSolver

    FallbackLeft --No--> Fail([Can't solve puzzle])

    TerminateLoop --No--> FindPattern[[Search for Pattern on the Sudoku grid \nthat lets us deduce \nwhat Candidates we can remove \nfrom neighboring Tiles]]
    FindPattern --> PatternFound{Pattern \nmatched?}

    PatternFound --No--> Increase

    PatternFound --Yes--> TryRemove[Check if there are any Candidates \nconcerned by the Pattern]
    TryRemove --> ToRemove{Concerned\ncandidates\nfound?}

    ToRemove --No--> Increase

    ToRemove --yes--> Remove[Remove Candidates]
    Remove --> Render{{Render Solving Step}}
    Render --> Trigger[Trigger Next Step]
    Trigger --> CleanUp[[Update Routine involving very basic Solving Algorithms]]
    CleanUp --> Increase

A Word of Caution#

Since there are some severe differences in between the implemented solving algorithms, the API does not force you (so far) to entirely stick to the prescription suggested by the diagram. For example, you are free to decide whether to implement a loop over tiles or to replace it by a better suiting approach.