public Dictionary <int, int> getCostMap(int cellId, WARGrid grid)
{
// the map itself
var map = new Dictionary <int, int>();
// Queue to store the cells to process starting with out target cellId
var opened = new Queue <enqueued>();
opened.Enqueue(new enqueued {
id = cellId, cost = 0
});
// the cells we've seen before
var closed = new HashSet <int>();
// make sure we dont come back to the origin
closed.Add(cellId);
// while we have cells left to process
while (opened.Count > 0)
{
// get the next cell to process
var cell = opened.Dequeue();
// assign the cost to the map
map.Add(cell.id, cell.cost);
foreach (var neighbor in grid.GetCell(cell.id).neighbors)
{
// if we're looking at a cell for the first time
if (!closed.Contains(neighbor))
{
// process their children
opened.Enqueue(new enqueued {
id = neighbor, cost = cell.cost + 1
});
// and add it to the list of cells we've processed
closed.Add(neighbor);
}
}
}
// return the map we just filled
return(map);
}
// calculate the final cell cost given our source, target and grid
private int cellCost(int cell, Dictionary <int, int> sourceCostMap, Dictionary <int, int> targetCostMap, WARGrid grid)
{
var cost = sourceCostMap[cell] + targetCostMap[cell];
return(cost); // + grid.GetCell(cell).pathFindingCost
}
public List <int> findPath(int source, int target, WARGrid grid)
{
// create the cost map for our source and target
var sourceCostMap = getCostMap(source, grid);
var targetCostMap = getCostMap(target, grid);
// traverse our grid using cost maps to determine path
// path to return
var path = new List <int>();
// map from cellId to the Node representing it
var nodeMap = new Dictionary <int, Node>();
nodeMap.Add(source, new Node(source));
// map to store the cell costs
var finalCostMap = new Dictionary <int, int>();
finalCostMap.Add(source, cellCost(source, sourceCostMap, targetCostMap, grid));
// set of nodes we need to process
var opened = new List <int> {
source
};
// set of nodes we have processed
var closed = new List <int>();
// while there are still cells to process
while (opened.Count > 0)
{
// find the cell with the lowest cost
var cell = opened.Aggregate(
(min, id) => {
return(finalCostMap[id] < finalCostMap[min] ? id : min);
}
);
// remove the cell with the lowest cost and add it to closed
opened.Remove(cell);
closed.Add(cell);
// if we found the current target then we have done our job
if (cell == target)
{
// create the path by walking parents of final node
path = getPathFromNodes(nodeMap[cell]).Select(node => node.id).ToList();
// then reverse it because we calculated the path from target to start
path.Reverse();
return(path);
}
// determine if we add our neighbors to the traversal path
foreach (var neighbor in grid.GetCell(cell).neighbors.Where(id => !closed.Contains(id)))
{
// if we have not opened this cell, or the path to this cell is shorter than previously found
if (!opened.Contains(neighbor) || getPathFromNodes(nodeMap[cell]).Count + 1 < getPathFromNodes(nodeMap[neighbor]).Count)
{
// add the neighbor to the nodeMap, linking its parent to the node at cell
nodeMap.Add(neighbor, new Node(neighbor, nodeMap[cell]));
// add the neighbor to the final cost map using cellCost
finalCostMap.Add(neighbor, cellCost(neighbor, sourceCostMap, targetCostMap, grid));
// if we haven't opened this neighbor already, open it
if (!opened.Contains(neighbor))
{
opened.Add(neighbor);
}
}
}
}
Debug.LogError("Reached end of Astar traversal without finding target");
return(path);
}
