persistable sclass FloodFill is Steppable { // input int w, h; swappable bool isConnectable(Pt a, Pt b) { throw unimplemented(); } void visited(Pt p) {} // internal new PtBuffer stack; BitMatrix visited; *(int *w, int *h) { visited = new BitSetMatrix(w, h); } *(int *w, int *h, BitMatrix *visited) {} selfType useQuadTree() { visited = new QuadTreeBitMatrix(w, h); this; } bool isPointVisited(Pt p) { ret visited.get(p); } void startAt aka addPoint(Pt p) { if (!isAddable(p)) ret; stack.add(p); addedPoint(p); } bool isValidPoint(Pt p) { ret p != null && !(p.x < 0 || p.y < 0 || p.x >= w || p.y >= h); } bool isAddable(Pt p) { if (!isValidPoint(p)) false; if (isPointVisited(p)) false; true; } void addedPoint(Pt p) {} public bool step() { if (empty(stack)) false; Pt p = popLast(stack); int x = p.x, y = p.y; visited.set(p, true); visited(p); possibleBridge(p, new Pt(x-1, y)); possibleBridge(p, new Pt(x+1, y)); possibleBridge(p, new Pt(x, y-1)); possibleBridge(p, new Pt(x, y+1)); true; } void possibleBridge(Pt a, Pt b) { if (isValidPoint(b) && isConnectable(a, b)) { addPoint(b); createBridge(a, b); } } void createBridge(Pt a, Pt b) {} void addAllPoints { for (p : allPointsInRect_virtual(w, h)) addPoint(p); } void doAllPoints { for (p : allPointsInRect_virtual(w, h)) { addPoint(p); stepAll(this); } } }