public static long AStarWithMinPathLengthCheck(Matrix matrix, IProfiler profiler = null)
{
if (profiler == null)
{
profiler = IProfiler.Default;
}
var minPathLengths = new long[matrix.NumCols, matrix.NumRows];
for (int col = 0; col < matrix.NumCols; ++col)
{
for (int row = 0; row < matrix.NumRows; ++row)
{
minPathLengths[col, row] = long.MaxValue;
}
}
var diagonalMins = Euler81.Program.DiagonalMins(matrix);
var diagonalMinSums = diagonalMins.Reverse().PartialSums().Reverse().Append(0).ToArray();
Func <SearchState, long> heuristicFunc = s => s.pathSum + diagonalMinSums[s.currentLocation.col + s.currentLocation.row + 1];
//Func<SearchState, long> heuristicFunc = s => s.pathSum; // assume all values are minimum value
Func <SearchState, IEnumerable <SearchState> > neighborFunc = s => NeighborFunc(s, matrix.NumCols, matrix.NumRows, heuristicFunc, minPathLengths);
Func <SearchState, bool> goalFunc = s => s.currentLocation.col == matrix.NumCols - 1 && s.currentLocation.row == matrix.NumRows - 1;
Euler.MinHeap <SearchState> searchFrontier = new Euler.MinHeap <SearchState>();
var startState = new SearchState
{
matrix = matrix,
currentLocation = (col : 0, row : 0),
locationsInPath = new HashSet <(int col, int row)>((col : 0, row : 0).Yield()),
pathSum = matrix[0, 0]
};
startState.heuristicValue = heuristicFunc(startState);
searchFrontier.Add(startState);
int numInspected = 0;
while (searchFrontier.Count > 0)
{
SearchState next;
using (profiler.Time("Pop search state"))
{
next = searchFrontier.Pop();
}
++numInspected;
if (numInspected % 1 == 0)
{
// TODO: progress
//Console.WriteLine($"{numInspected}/{numInspected+searchFrontier.Count}: {next.currentLocation}, {next.locationsInPath.Count}, {next.pathSum}, {next.heuristicValue}");
}
if (goalFunc(next))
{
// TODO: progress
//Console.WriteLine($"Goal reached. Path sum: {next.pathSum}");
return(next.pathSum);
}
else
{
using (profiler.Time("Get neighbors and add to heap"))
searchFrontier.AddRange(neighborFunc(next));
}
}
throw new Exception("Goal state not reached!");
}
