static bool Solve()
{
var(h, w) = Read2();
var s = GridShortestPath.ReadEnclosedGrid(ref h, ref w);
var sv = GridShortestPath.FindChar(s, 's');
var ev = GridShortestPath.FindChar(s, 'g');
var r = GridShortestPath.UndirectedBfs(h, w, s, sv, ev);
return(r.GetByP(ev) < int.MaxValue);
}
static void Main()
{
var(h, w) = Read2();
var sv = Read2() - new P(1, 1);
var ev = Read2() - new P(1, 1);
var s = Array.ConvertAll(new bool[h], _ => Console.ReadLine());
var r = GridShortestPath.UndirectedBfs(h, w, s, sv, ev);
Console.WriteLine(r.GetByP(ev));
}
static void Main()
{
var(h, w) = Read2();
var s = Array.ConvertAll(new bool[h], _ => Console.ReadLine());
var sv = GridShortestPath.FindChar(h, w, s, 'S');
var gv = GridShortestPath.FindChar(h, w, s, 'G');
var map = new Dictionary <char, List <P> >();
for (char c = 'a'; c <= 'z'; c++)
{
map[c] = new List <P>();
}
for (int i = 0; i < h; i++)
{
for (int j = 0; j < w; j++)
{
var c = s[i][j];
if ('a' <= c && c <= 'z')
{
map[c].Add(new P(i, j));
}
}
}
var r = GridShortestPath.Bfs(h, w, v =>
{
var c = s[v.i][v.j];
if (!map.ContainsKey(c))
{
return(v.Nexts());
}
var nvs = v.Nexts().Concat(map[c]).ToArray();
map.Remove(c);
return(nvs);
},
sv, gv, v => s[v.i][v.j] == '#').GetByP(gv);
Console.WriteLine(r == int.MaxValue ? -1 : r);
}