static string TracePath(Maze_element elem)
{
//Console.WriteLine("Tracing...");
string path = "";
var tmp = elem;
while (tmp.fromNode != null)
{
var par = tmp.fromNode;
if (par.x < tmp.x)
{
path = "S" + path;
}
else if (par.x > tmp.x)
{
path = "N" + path;
}
else if (par.y < tmp.y)
{
path = "E" + path;
}
else if (par.y > tmp.y)
{
path = "W" + path;
}
tmp = par;
}
return(path);
}
public Maze_element(int i, int j)
{
x = i;
y = j;
f = Int32.MaxValue;
g = Int32.MaxValue;
h = 0;
heapIndex = -1;
fromNode = null;
}
public void Add(Maze_element element)
{
if (_size == _elements.Length)
{
throw new IndexOutOfRangeException();
}
_elements[_size] = element;
element.heapIndex = _size;
_size++;
ReCalculateUp(_size - 1);
}
static string A_star_pathFinder(List <List <string> > Maze, int Ax, int Ay, int Bx, int By)
{
//Console.WriteLine("Start A*");
string pathResult = "";
List <List <Maze_element> > MazeObj = new List <List <Maze_element> >();
int n = Maze.Count;
int m = Maze[0].Count;
MinHeapClass MinHeap = new MinHeapClass(n * m);
for (int i = 0; i < n; i++)
{
List <Maze_element> tmpArr = new List <Maze_element>();
for (int j = 0; j < m; j++)
{
Maze_element elem = new Maze_element(i, j);
elem.h = Math.Abs(i - Bx) + Math.Abs(j - By);
if ((i == Ax) && (j == Ay))
{
elem.g = 0;
elem.f = elem.g + elem.h;
}
tmpArr.Add(elem);
if (Maze[i][j] != "X")
{
MinHeap.Add(elem);
}
}
MazeObj.Add(tmpArr);
}
Console.WriteLine(MinHeap.Peek().f);
bool stop = false;
do
{
Maze_element elem = MinHeap.Pop();
//Scan 4 adjacent block
int[] compass = { -1, 0, 1, 0, -1 };
for (int i = 0; i < 4; i++)
{
int x = elem.x + compass[i];
int y = elem.y + compass[i + 1];
if ((x < 0) || (y < 0))
{
continue;
}
if ((x >= n) || (y >= m))
{
continue;
}
if (Maze[x][y] == "X")
{
continue;
}
if (MazeObj[x][y].f > elem.g + 1 + MazeObj[x][y].h)
{
MazeObj[x][y].g = elem.g + 1;
MazeObj[x][y].f = MazeObj[x][y].g + MazeObj[x][y].h;
MazeObj[x][y].fromNode = elem;
var heapIndex = MazeObj[x][y].heapIndex;
MinHeap.ReCalculateUp(heapIndex);
MinHeap.ReCalculateDown(heapIndex);
}
if ((x == Bx) && (y == By))
{
stop = true;
//Console.WriteLine("Found B");
pathResult = TracePath(MazeObj[x][y]);
break;
}
}
if (stop)
{
break;
}
} while (!MinHeap.IsEmpty());
return(pathResult);
}
