public WorldState Update(Direction direction)
{
var tailEnd = Snake.GetTailEnd();
Snake.Move(direction);
if (options.WarpAroundEdges)
{
for (int i = 0; i < Snake.Count; i++)
{
var body = Snake[i];
Snake[i] = ((Size.X + body.X) % Size.X, (Size.Y + body.Y) % Size.Y);
}
}
if (Snake.IsInvalidState(Size))
{
return(WorldState.Invalid);
}
var head = Snake.GetHead();
// Grow if apple is inside snake and create another apple
if (head == Apple)
{
Snake.Add(tailEnd);
// memory vs processing speed? the classic optimization decision.
// from a range containing all possible values in grid without the ones by snake.
var notSnake = Size.Range().Where((p) => !Snake.Contains(p)).ToList();
if (notSnake.Count <= 0)
{
return(WorldState.Won);
}
else
{
// try to generate apple to be near snake head, or the game will be boring
// get inclusive lower bound and inclusive upper bound of coordinates close to snake head, within size
int xOffset = Size.X / 10;
int x0 = (head.X - xOffset).EnsuredWithin();
int x1 = (head.X + xOffset).EnsuredWithin(Size.X);
int yOffset = Size.Y / 10;
int y0 = (head.Y - xOffset).EnsuredWithin();
int y1 = (head.Y + xOffset).EnsuredWithin(Size.Y);
var nearHead = notSnake.Where((p) => p.X >= x0 && p.X <= x1 && p.Y >= y0 && p.Y <= y1).ToArray();
if (nearHead.Length > 0)
{
Apple = nearHead[rand.Next(nearHead.Length)];
}
else if (notSnake.Count == 1)
{
Apple = notSnake[0];
}
else
{
// pick number closer to snake head more likely
// sort closest to snake head first
notSnake.Sort((point1, point2) => point1.CompareTo(point2, head));
// https://stackoverflow.com/a/9956791/12347502 reference
// https://github.com/Stiles-X/WeightedRandomSelector switch to this if things get messy
// we want [0,1]
// [2, 1]
var discreteChunks = Enumerable.Range(1, notSnake.Count + 1).Reverse().ToArray();
// [2, 3]
var distribution = new int[discreteChunks.Length];
{
int current = distribution[0] = discreteChunks[0];
for (int i = 1; i < distribution.Length; i++)
{
distribution[i] = current += discreteChunks[i];
}
}
// linear search
int max = distribution[^ 1];
