private static Point[][] boolsToPaths(Virtual2DArray <bool> input)
{
int width = input.Width;
int height = input.Height;
var results = new List <Point[]>();
var visitedUpArrow = Ut.NewArray <bool>(width, height);
for (int i = 0; i < width; i++)
{
for (int j = 0; j < height; j++)
{
// every region must have at least one up arrow (left edge)
if (!visitedUpArrow[i][j] && input.Get(i, j) && !input.Get(i - 1, j))
{
results.Add(tracePolygon(input, i, j, visitedUpArrow));
}
}
}
return(results.ToArray());
}
private static Point[] tracePolygon(Virtual2DArray <bool> input, int i, int j, bool[][] visitedUpArrow)
{
var result = new List <Point>();
var dir = Direction.Up;
while (true)
{
// In each iteration of this loop, we move from the current edge to the next one.
// We have to prioritise right-turns so that the diagonal-adjacent case is handled correctly.
// Every time we take a 90° turn, we add the corner coordinate to the result list.
// When we get back to the original edge, the polygon is complete.
switch (dir)
{
case Direction.Up:
// If we’re back at the beginning, we’re done with this polygon
if (visitedUpArrow[i][j])
{
return(result.ToArray());
}
visitedUpArrow[i][j] = true;
if (!input.Get(i, j - 1))
{
result.Add(new Point(i, j));
dir = Direction.Right;
}
else if (input.Get(i - 1, j - 1))
{
result.Add(new Point(i, j));
dir = Direction.Left;
i--;
}
else
{
j--;
}
break;
case Direction.Down:
j++;
if (!input.Get(i - 1, j))
{
result.Add(new Point(i, j));
dir = Direction.Left;
i--;
}
else if (input.Get(i, j))
{
result.Add(new Point(i, j));
dir = Direction.Right;
}
break;
case Direction.Left:
if (!input.Get(i - 1, j - 1))
{
result.Add(new Point(i, j));
dir = Direction.Up;
j--;
}
else if (input.Get(i - 1, j))
{
result.Add(new Point(i, j));
dir = Direction.Down;
}
else
{
i--;
}
break;
case Direction.Right:
i++;
if (!input.Get(i, j))
{
result.Add(new Point(i, j));
dir = Direction.Down;
}
else if (input.Get(i, j - 1))
{
result.Add(new Point(i, j));
dir = Direction.Up;
j--;
}
break;
}
}
}