Trail · techniques

Three patterns. Then everything.

Trace one continuous path through every cell, in checkpoint order. The hard part is avoiding orphans.

Forced corners

Cells with only two neighbors (corners, then edges) often force you into one direction or the other. Look at them first.

Corners are entry-points with only two onward neighbors. Often one of them is forced because the other would orphan part of the board.

Dead-end avoidance

When a cell’s only unvisited neighbor is one cell, that cell must be entered from there or it’ll be orphaned — unreachable for the rest of the path.

(1,0) now has just one unvisited neighbor — if you don't reach it next, it's orphaned. Look for these cells before they trap you.

Between-checkpoint counting

Each segment between two consecutive checkpoints has a fixed cell count. If geometry forces more cells into a segment than should fit, the route must change.

Each segment between consecutive checkpoints has a fixed cell budget. Count what must fit; if the geometry forces more than the budget, you know the segment must take a different route.

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