/// <summary>
/// If multiple paths are existing to a square, at a branch, always chose the first one in the X,Y order.
/// </summary>
public static Path SearchOptimalPath(VisitedSquare to)
{
var ret = new Path();
var current = to;
while (current.VisitedFrom != null)
{
ret.Steps.AddFirst(current.Coordinate);
current = current.VisitedFrom.OrderBy(sq => sq.Coordinate.X).ThenBy(sq => sq.Coordinate.Y).First();
}
return(ret);
}
/// <summary>
/// Searches for the shortest path for each reachable enemy's adjacent square.
/// </summary>
static public IDictionary <Player, List <Path> > ReachableEnemiesAndShortestPaths(Map map, Player fromPlayer)
{
bool newSquareVisitedThisStep = true;
List <VisitedSquare> visitedSquares = new List <VisitedSquare>()
{
new VisitedSquare()
{
Coordinate = fromPlayer.Location,
VisitedFrom = null,
InStep = 0
}
};
int currentStep = 1;
var wallLocations = map.Walls.Select(w => w.Location);
var playerLocations = map.Players.Select(p => p.Location);
// Visit the map starting from the given location
// Create a structure where the visited squares are stored
// also store that in which step they have been visited and from which square
while (newSquareVisitedThisStep)
{
newSquareVisitedThisStep = false;
var squaresFromLastStep = visitedSquares.Where(vs => vs.InStep == currentStep - 1).ToList();
var squaresAlreadyVisitedBeforeCurrentStep = visitedSquares.Select(s => s.Coordinate).ToList();
foreach (var square in squaresFromLastStep)
{
var possiblenewCoordinates = new List <Coordinate>()
{
new Coordinate(square.Coordinate.X + 1, square.Coordinate.Y),
new Coordinate(square.Coordinate.X - 1, square.Coordinate.Y),
new Coordinate(square.Coordinate.X, square.Coordinate.Y + 1),
new Coordinate(square.Coordinate.X, square.Coordinate.Y - 1),
};
foreach (var newCoordinate in possiblenewCoordinates)
{
if (wallLocations.Contains(newCoordinate) || playerLocations.Contains(newCoordinate) || squaresAlreadyVisitedBeforeCurrentStep.Contains(newCoordinate))
{
continue;
}
var visitedSquare = visitedSquares.FirstOrDefault(sq => sq.Coordinate == newCoordinate);
if (visitedSquare == null)
{
var squareToAdd = new VisitedSquare()
{
Coordinate = newCoordinate,
InStep = currentStep,
};
squareToAdd.VisitedFrom.Add(square);
visitedSquares.Add(squareToAdd);
}
else // square has been already visited from an other square in this step
{
visitedSquare.VisitedFrom.Add(square);
}
newSquareVisitedThisStep = true;
}
}
currentStep++;
}
// Calculate the squares which are adjacent to enemies
// and they can be possibly reached (no wall, no other player unless its the current player already standing there)
var adjacentPossiblyReachableSquaresToEnemies = new Dictionary <Player, List <Coordinate> >();
var enemies = map.Players.Where(p => p.Team != fromPlayer.Team);
foreach (var enemy in enemies)
{
var enemyLocation = enemy.Location;
adjacentPossiblyReachableSquaresToEnemies.Add(enemy, new List <Coordinate>());
var rightSquare = new Coordinate(enemyLocation.X + 1, enemyLocation.Y);
if ((!wallLocations.Contains(rightSquare) && !playerLocations.Contains(rightSquare)) ||
rightSquare == fromPlayer.Location)
{
adjacentPossiblyReachableSquaresToEnemies[enemy].Add(rightSquare);
}
var leftSquare = new Coordinate(enemyLocation.X - 1, enemyLocation.Y);
if ((!wallLocations.Contains(leftSquare) && !playerLocations.Contains(leftSquare)) ||
leftSquare == fromPlayer.Location)
{
adjacentPossiblyReachableSquaresToEnemies[enemy].Add(leftSquare);
}
var upSquare = new Coordinate(enemyLocation.X, enemyLocation.Y + 1);
if ((!wallLocations.Contains(upSquare) && !playerLocations.Contains(upSquare)) ||
upSquare == fromPlayer.Location)
{
adjacentPossiblyReachableSquaresToEnemies[enemy].Add(upSquare);
}
var downSquare = new Coordinate(enemyLocation.X, enemyLocation.Y - 1);
if ((!wallLocations.Contains(downSquare) && !playerLocations.Contains(downSquare)) ||
downSquare == fromPlayer.Location)
{
adjacentPossiblyReachableSquaresToEnemies[enemy].Add(downSquare);
}
}
// search these adjacent square in the visit structure.
// Create the optimal path to each of them.
var enemiesWithPathsToAdjacentSquares = new Dictionary <Player, List <Path> >();
foreach (KeyValuePair <Player, List <Coordinate> > enemyWithAdjacentSqures in adjacentPossiblyReachableSquaresToEnemies)
{
foreach (Coordinate adjSquare in enemyWithAdjacentSqures.Value)
{
var visited = visitedSquares.FirstOrDefault(vs => vs.Coordinate == adjSquare);
if (visited != null)
{
var paths = SearchOptimalPath(visited);
if (!enemiesWithPathsToAdjacentSquares.ContainsKey(enemyWithAdjacentSqures.Key))
{
enemiesWithPathsToAdjacentSquares.Add(enemyWithAdjacentSqures.Key, new List <Path>());
}
enemiesWithPathsToAdjacentSquares[enemyWithAdjacentSqures.Key].Add(paths);
}
}
}
// Out of all reachable adjacent squares of an enemy, search the shortest ones, and return them
var enemiesWithPathsToClosestAdjacentSquares = new Dictionary <Player, List <Path> >();
foreach (var item in enemiesWithPathsToAdjacentSquares)
{
int minLength = item.Value.Min(p => p.Length);
enemiesWithPathsToClosestAdjacentSquares.Add(item.Key, item.Value.Where(p => p.Length == minLength).ToList());
}
return(enemiesWithPathsToClosestAdjacentSquares);
}