public static HashSet <UEdge2i> ConnectedCells_ExpansionEdges_Set( this PM_Maze maze ) { HashSet <UEdge2i> expansionEdges = new HashSet <UEdge2i>(); HashSet <Vec2i> connectedCells = maze.ConnectedCells_Set(); foreach (var cell in connectedCells) { if (maze.Q_Is_Cell_Connected(cell)) { expansionEdges.UnionWith(maze.Cell_ExpansionEdges_Set(cell)); } } return(expansionEdges); }