/// <summary> 搜索下一个坐标点 </summary>
private static void SearchPoint(AStarPoint curPoint, AStarPoint nextPoint)
{
// 不可到达或在 CloseList 中则返回
if (!nextPoint.IsReachable || CloseList.Contains(nextPoint))
{
return;
}
// next 不在 OpenList 中
if (!OpenList.Contains(nextPoint))
{
// 将 next 加入 OpenList
OpenList.AddLast(nextPoint);
// 设置 next 的父节点
nextPoint.Parent = curPoint;
// 计算 next 的 G 值
nextPoint.G = curPoint.G + 1;
}
// next 在 OpenList 中，且新的 G 值更小
else if (curPoint.G + 1 < nextPoint.G)
{
// 设置 next 的父节点
nextPoint.Parent = curPoint;
// 计算 next 的 G 值
nextPoint.G = curPoint.G + 1;
}
}
public static IEnumerable <Vector2Int> GetPath(Block[][] blocks, Vector2Int start, Vector2Int end)
{
// 判断目标坐标是否可到达，不可到达则直接返回
Block block = blocks[end.x][end.y];
if (!block.Reachable)
{
return(null);
}
// 根据 blocks 构造 points
AStarPoint[][] points = new AStarPoint[blocks.Length][];
for (int i = 0; i < points.Length; i++)
{
points[i] = new AStarPoint[blocks[i].Length];
for (int j = 0; j < points[i].Length; j++)
{
points[i][j] = new AStarPoint(blocks[i][j].Coords, blocks[i][j].Reachable, end);
}
}
bool pathIsFound = false; // 路径标识
OpenList = new LinkedList <AStarPoint>();
CloseList = new LinkedList <AStarPoint>();
// 将起始点加入 OpenList
OpenList.AddLast(points[start.x][start.y]);
// 循环条件：OpenList 不为空且还未找到路径
while (OpenList.Count != 0 && !pathIsFound)
{
// 找到 F 值最小的 point
AStarPoint point = null;
foreach (var item in OpenList)
{
if (point == null || point.F >= item.F)
{
point = item;
}
}
// 将 point 移出 OpenList，加入 CloseList
OpenList.Remove(point);
CloseList.AddLast(point);
// 依次搜索周围四个点
foreach (var delta in OFFSET_COORDS)
{
Vector2Int nextCoords = point.Coords + delta;
// 坐标不合法则返回
if (!MapUIUtil.IsBlockReachable(blocks, nextCoords))
{
continue;
}
// 搜索 next
AStarPoint nextPoint = points[nextCoords.x][nextCoords.y];
SearchPoint(point, nextPoint);
// 搜索点为 end 说明找到路径了，直接跳出循环
if (nextPoint.Coords == end)
{
pathIsFound = true;
break;
}
}
}
// 未找到路径则返回 null
if (!pathIsFound)
{
return(null);
}
// 找到路径则从 end 开始依次读取父节点并加入 path，最后返回 path
LinkedList <Vector2Int> path = new LinkedList <Vector2Int>();
AStarPoint wayPoint = points[end.x][end.y];
while (wayPoint != null)
{
path.AddFirst(wayPoint.Coords);
wayPoint = wayPoint.Parent;
}
return(path);
}
