static List<Pair> findPath(bool[,] map)
{
Dir[,] dirMap = new Dir[map.GetLength(0), map.GetLength(1)];
bool stuck = false;
for (int i = 0; i < dirMap.GetLength(0); i++)
{
if (stuck)
dirMap[i, 0] = new Dir(0, Direction.impossible);
else if (map[0, i])
dirMap[i, 0] = new Dir(1, Direction.down);
else
{
stuck = true;
dirMap[i, 0] = new Dir(0, Direction.impossible);
}
}
stuck = false;
for (int i = 0; i < dirMap.GetLength(1); i++)
{
if (stuck)
dirMap[0, i] = new Dir(0, Direction.impossible);
else if (map[0, i])
dirMap[0, i] = new Dir(1, Direction.right);
else
{
stuck = true;
dirMap[0, i] = new Dir(0, Direction.impossible);
}
}
//Build the map bottom up.
for (int i = 1; i < map.GetLength(0); i++)
{
for (int j = 1; j < map.GetLength(1); j++)
{
if (!map[i, j])
{
dirMap[i, j] = new Dir(0, Direction.impossible);
continue;
}
Dir up = dirMap[i - 1, j];
Dir left = dirMap[i, j - 1];
if (up.directions != Direction.impossible && left.directions != Direction.impossible)
dirMap[i, j] = new Dir(up.count + left.count, Direction.both);
else if (left.directions != Direction.impossible)
dirMap[i, j] = new Dir(left.count, Direction.right);
else if (up.directions != Direction.impossible)
dirMap[i, j] = new Dir(up.count, Direction.down);
else
dirMap[i, j] = new Dir(0, Direction.impossible);
}
}
//Trace back.
int possibilities = dirMap[dirMap.GetLength(0) - 1, dirMap.GetLength(1) - 1].count;
List<Pair> path = new List<Pair>();
int x = dirMap.GetLength(0) - 1;
int y = dirMap.GetLength(0) - 1;
while (x != 0 || y != 0)
{
path.Add(new Pair(x, y));
Dir current = dirMap[x, y];
if (current.directions == Direction.down)
x--;
else if (current.directions == Direction.right)
y--;
else if (current.directions == Direction.both)
x--;//It can be y-- here as well because both ways work
else
return null;//Impossible to reach.
}
path.Reverse();
return path;
}
static List <Pair> findPath(bool[,] map)
{
Dir[,] dirMap = new Dir[map.GetLength(0), map.GetLength(1)];
bool stuck = false;
for (int i = 0; i < dirMap.GetLength(0); i++)
{
if (stuck)
{
dirMap[i, 0] = new Dir(0, Direction.impossible);
}
else if (map[0, i])
{
dirMap[i, 0] = new Dir(1, Direction.down);
}
else
{
stuck = true;
dirMap[i, 0] = new Dir(0, Direction.impossible);
}
}
stuck = false;
for (int i = 0; i < dirMap.GetLength(1); i++)
{
if (stuck)
{
dirMap[0, i] = new Dir(0, Direction.impossible);
}
else if (map[0, i])
{
dirMap[0, i] = new Dir(1, Direction.right);
}
else
{
stuck = true;
dirMap[0, i] = new Dir(0, Direction.impossible);
}
}
//Build the map bottom up.
for (int i = 1; i < map.GetLength(0); i++)
{
for (int j = 1; j < map.GetLength(1); j++)
{
if (!map[i, j])
{
dirMap[i, j] = new Dir(0, Direction.impossible);
continue;
}
Dir up = dirMap[i - 1, j];
Dir left = dirMap[i, j - 1];
if (up.directions != Direction.impossible && left.directions != Direction.impossible)
{
dirMap[i, j] = new Dir(up.count + left.count, Direction.both);
}
else if (left.directions != Direction.impossible)
{
dirMap[i, j] = new Dir(left.count, Direction.right);
}
else if (up.directions != Direction.impossible)
{
dirMap[i, j] = new Dir(up.count, Direction.down);
}
else
{
dirMap[i, j] = new Dir(0, Direction.impossible);
}
}
}
//Trace back.
int possibilities = dirMap[dirMap.GetLength(0) - 1, dirMap.GetLength(1) - 1].count;
List <Pair> path = new List <Pair>();
int x = dirMap.GetLength(0) - 1;
int y = dirMap.GetLength(0) - 1;
while (x != 0 || y != 0)
{
path.Add(new Pair(x, y));
Dir current = dirMap[x, y];
if (current.directions == Direction.down)
{
x--;
}
else if (current.directions == Direction.right)
{
y--;
}
else if (current.directions == Direction.both)
{
x--;//It can be y-- here as well because both ways work
}
else
{
return(null);//Impossible to reach.
}
}
path.Reverse();
return(path);
}