public List <Cell> GetAvailableNeighbors(int timeunit)
{
var allNeighbors = GetNeighbors();
var availableNeighbors = new List <Cell>();
foreach (var neighbor in allNeighbors)
{
if (!grid.ReservationTable.ContainsKey(new Grid.CellTimePair(neighbor, timeunit)))
{
// head to head collision prevention
var neighborReservation = new Grid.CellTimePair(neighbor, timeunit - 1);
if (grid.ReservationTable.ContainsKey(neighborReservation))
{
var neighborStudent = grid.ReservationTable[neighborReservation];
var cellNextReservation = new Grid.CellTimePair(this, timeunit);
if (grid.ReservationTable.ContainsKey(cellNextReservation) && grid.ReservationTable[cellNextReservation] == neighborStudent)
{
// head-to-head collision detected
continue;
}
}
availableNeighbors.Add(neighbor);
}
}
return(availableNeighbors);
}
private List <Grid.CellTimePair> GetPath(Cell startCell, Cell destinationCell, int startTimeUnit = 0)
{
// implementation of A star
// a timeunit represents one movement
var grid = GameManager.Grid;
if (startCell == null)
{
throw new System.NullReferenceException("Student is not in grid");
}
var rra = getRRA(startCell, destinationCell);
var queue = new PriorityQueue <Grid.CellTimePair>();
var startCellTime = new Grid.CellTimePair(startCell, startTimeUnit);
queue.Enqueue(startCellTime, 0);
var pathParents = new Dictionary <Grid.CellTimePair, Grid.CellTimePair>();
while (!queue.IsEmpty())
{
var currentCellTimePair = queue.Peek();
var currentCell = currentCellTimePair.cell;
if (currentCellTimePair.timeUnit - startTimeUnit == searchDepth || currentCell == destinationCell)
{
break;
}
queue.Dequeue();
var neighborGCost = currentCellTimePair.timeUnit + 1;
foreach (var neighborCell in currentCell.GetAvailableNeighbors(neighborGCost))
{
var neighborCellTimePair = new Grid.CellTimePair(neighborCell, neighborGCost);
var neighborHCost = rra.GetTrueDistance(neighborCell);
pathParents[neighborCellTimePair] = currentCellTimePair;
queue.Enqueue(neighborCellTimePair, neighborGCost + neighborHCost);
}
}
var path = new List <Grid.CellTimePair>();
if (queue.IsEmpty()) // path not found
{
path.Add(new Grid.CellTimePair(startCell, startTimeUnit + 1));
path.Add(new Grid.CellTimePair(startCell, startTimeUnit + 2));
path.Add(new Grid.CellTimePair(startCell, startTimeUnit + 3));
return(path);
}
var destinationCellTimePair = queue.Peek();
var parent = destinationCellTimePair;
while (pathParents.ContainsKey(parent))
{
GameManager.Grid.ReservationTable.Add(parent, this);
path.Add(parent);
parent = pathParents[parent];
}
path.Reverse();
return(path);
}
private List <Grid.CellTimePair> GetIdlePath(Cell idleCell, int idleTime, int startTimeUnit = 0)
{
// a star that favors staying at the current cell
var grid = GameManager.Grid;
if (idleCell == null)
{
throw new System.NullReferenceException("Student is not in grid");
}
var queue = new PriorityQueue <Grid.CellTimePair>();
var startCellTime = new Grid.CellTimePair(idleCell, startTimeUnit);
queue.Enqueue(startCellTime, 0);
var pathParents = new Dictionary <Grid.CellTimePair, Grid.CellTimePair>();
var currentIdleTime = 0;
while (!queue.IsEmpty())
{
var currentCellTimePair = queue.Peek();
var currentCell = currentCellTimePair.cell;
if (currentCell == idleCell && ++currentIdleTime >= idleTime)
{
break;
}
queue.Dequeue();
var time = currentCellTimePair.timeUnit + 1;
foreach (var neighborCell in currentCell.GetAvailableNeighbors(time))
{
var neighborCellTimePair = new Grid.CellTimePair(neighborCell, time);
var neighborHCost = Cell.ManhanttanDistance(neighborCell, idleCell);
pathParents[neighborCellTimePair] = currentCellTimePair;
queue.Enqueue(neighborCellTimePair, neighborHCost);
}
}
var path = new List <Grid.CellTimePair>();
if (queue.IsEmpty()) // path not found
{
path.Add(new Grid.CellTimePair(idleCell, startTimeUnit + 1));
path.Add(new Grid.CellTimePair(idleCell, startTimeUnit + 2));
path.Add(new Grid.CellTimePair(idleCell, startTimeUnit + 3));
return(path);
}
var destinationCellTimePair = queue.Peek();
var parent = destinationCellTimePair;
while (pathParents.ContainsKey(parent))
{
GameManager.Grid.ReservationTable.Add(parent, this);
path.Add(parent);
parent = pathParents[parent];
}
path.Reverse();
return(path);
}
