int FindStaircaseStart(Point[] pts, out bool canHaveStaircase) {
canHaveStaircase = false;
if (pts.Length < 5) // At least five points make a staircase
return -1;
var segs = new[] {
new SegWithIndex(pts, 0), new SegWithIndex(pts, 1), new SegWithIndex(pts, 2),
new SegWithIndex(pts, 3)
};
int segToReplace = 0;
for (int i = 0;;) {
bool canHaveStaircaseAtI;
if (IsStaircase(pts, i, segs, out canHaveStaircaseAtI)) {
canHaveStaircase = true;
return i;
}
canHaveStaircase = canHaveStaircase || canHaveStaircaseAtI;
i++;
if (pts.Length < i + 5)// At least five points make a staircase
return -1;
segs[segToReplace] = new SegWithIndex(pts, i + 3);
segToReplace += 1;
segToReplace %= 4;
}
}
int FindStaircaseStart(Point[] pts, out bool canHaveStaircase)
{
canHaveStaircase = false;
if (pts.Length < 5) // At least five points make a staircase
{
return(-1);
}
var segs = new[] {
new SegWithIndex(pts, 0), new SegWithIndex(pts, 1), new SegWithIndex(pts, 2),
new SegWithIndex(pts, 3)
};
int segToReplace = 0;
for (int i = 0;;)
{
bool canHaveStaircaseAtI;
if (IsStaircase(pts, i, segs, out canHaveStaircaseAtI))
{
canHaveStaircase = true;
return(i);
}
canHaveStaircase = canHaveStaircase || canHaveStaircaseAtI;
i++;
if (pts.Length < i + 5)// At least five points make a staircase
{
return(-1);
}
segs[segToReplace] = new SegWithIndex(pts, i + 3);
segToReplace += 1;
segToReplace %= 4;
}
}
/// <summary>
/// ignoring crossing at a
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <param name="segsToIgnore"></param>
/// <returns></returns>
bool Crossing(Point a, Point b, SegWithIndex[] segsToIgnore) {
return IsCrossing(new LineSegment(a, b), segTree, segsToIgnore);
}
static Rectangle Rect(SegWithIndex seg) {
return new Rectangle(seg.Start,seg.End);
}
void InsSeg(Point[] pts, int i) {
var seg = new SegWithIndex(pts, i);
segTree.Add(Rect(seg), seg);
}
void RemoveSeg(SegWithIndex seg) {
segTree.Remove(Rect(seg), seg);
}
bool IsStaircase(Point[] pts, int offset, SegWithIndex[] segsToIgnore, out bool canHaveStaircaseAtI) {
var a = pts[offset];
var b = pts[offset + 1];
var c = pts[offset + 2];
var d = pts[offset + 3];
var f = pts[offset + 4];
canHaveStaircaseAtI = false;
if (CompassVector.DirectionsFromPointToPoint(a, b) != CompassVector.DirectionsFromPointToPoint(c, d) ||
CompassVector.DirectionsFromPointToPoint(b, c) != CompassVector.DirectionsFromPointToPoint(d, f))
return false;
c = GetFlippedPoint(pts, offset);
if (IntersectObstacleHierarchy(b, c, d))
return false;
canHaveStaircaseAtI = true;
return !Crossing(b, c, segsToIgnore);
}
/// <summary>
/// ignoring crossing at ls.Start
/// </summary>
/// <param name="ls"></param>
/// <param name="rTree"></param>
/// <param name="segsToIgnore"></param>
/// <returns></returns>
static bool IsCrossing(LineSegment ls, RTree<SegWithIndex> rTree, SegWithIndex[] segsToIgnore) {
return rTree.GetAllIntersecting(ls.BoundingBox).Where(seg => !segsToIgnore.Contains(seg)).Any();
}
static Rectangle Rect(SegWithIndex seg)
{
return(new Rectangle(seg.Start, seg.End));
}
void InsSeg(Point[] pts, int i)
{
var seg = new SegWithIndex(pts, i);
segTree.Add(Rect(seg), seg);
}
void RemoveSeg(SegWithIndex seg)
{
segTree.Remove(Rect(seg), seg);
}