/**
* Calculate the shortest path using a simple A-Star algorithm.
* The unit information and movement type must have already been set.
* The path information is set only if a valid path is found.
* @param startPosition The position to start from.
* @param endPosition The position we want to reach.
* @return True if a path exists, false otherwise.
*/
bool Pathfinding::aStarPath(const Position &startPosition, const Position &endPosition)
{
// reset every node, so we have to check them all
for (std::vector<PathfindingNode>::iterator it = _nodes.begin(); it != _nodes.end(); ++it)
it->reset();
// start position is the first one in our "open" list
PathfindingNode *start = getNode(startPosition);
start->connect(0, 0, 0, endPosition);
PathfindingOpenSet openList;
openList.push(start);
// if the open list is empty, we've reached the end
while(!openList.empty())
{
PathfindingNode *currentNode = openList.pop();
Position const ¤tPos = currentNode->getPosition();
currentNode->setChecked();
if (currentPos == endPosition) // We found our target.
{
_path.clear();
PathfindingNode *pf = currentNode;
while (pf->getPrevNode())
{
_path.push_back(pf->getPrevDir());
pf = pf->getPrevNode();
}
return true;
}
// Try all reachable neighbours.
for (int direction = 0; direction < 10; direction++)
{
Position nextPos;
int tuCost = getTUCost(currentPos, direction, &nextPos, _unit);
if (tuCost == 255) // Skip unreachable / blocked
continue;
PathfindingNode *nextNode = getNode(nextPos);
if (nextNode->isChecked()) // Our algorithm means this node is already at minimum cost.
continue;
int totalTuCost = currentNode->getTUCost() + tuCost;
// If this node is unvisited or visited from a better path.
if (!nextNode->inOpenSet() || nextNode->getTUCost() > totalTuCost)
{
nextNode->connect(totalTuCost, currentNode, direction, endPosition);
openList.push(nextNode);
}
}
}
// Unble to reach the target
return false;
}
/**
* Use Dijkstra's algorithm to locate all tiles reachable to @a *unit with a TU cost no more than @a tuMax.
* @param unit Pointer to the unit.
* @param tuMax The maximum cost of the path to each tile.
* @return An array of reachable tiles, sorted in ascending order of cost. The first tile is the start location.
*/
std::vector<int> Pathfinding::findReachable(BattleUnit *unit, int tuMax)
{
const Position &start = unit->getPosition();
for (std::vector<PathfindingNode>::iterator it = _nodes.begin(); it != _nodes.end(); ++it)
{
it->reset();
}
PathfindingNode *startNode = getNode(start);
startNode->connect(0, 0, 0);
PathfindingOpenSet unvisited;
unvisited.push(startNode);
std::vector<PathfindingNode*> reachable;
while (!unvisited.empty())
{
PathfindingNode *currentNode = unvisited.pop();
Position const ¤tPos = currentNode->getPosition();
// Try all reachable neighbours.
for (int direction = 0; direction < 10; direction++)
{
Position nextPos;
int tuCost = getTUCost(currentPos, direction, &nextPos, unit);
if (tuCost == 255) // Skip unreachable / blocked
continue;
if (tuCost > tuMax) // Run out of TUs
continue;
PathfindingNode *nextNode = getNode(nextPos);
if (nextNode->isChecked()) // Our algorithm means this node is already at minimum cost.
continue;
int totalTuCost = currentNode->getTUCost() + tuCost;
// If this node is unvisited or visited from a better path.
if (!nextNode->inOpenSet() || nextNode->getTUCost() > totalTuCost)
{
nextNode->connect(totalTuCost, currentNode, direction);
unvisited.push(nextNode);
}
}
currentNode->setChecked();
reachable.push_back(currentNode);
}
std::sort(reachable.begin(), reachable.end(), MinNodeCosts());
std::vector<int> tiles;
tiles.reserve(reachable.size());
for (std::vector<PathfindingNode*>::const_iterator it = reachable.begin(); it != reachable.end(); ++it)
{
tiles.push_back(_save->getTileIndex((*it)->getPosition()));
}
return tiles;
}
