string Solve(int K, int N, List <int> keys, List <Chest> chests)
{
VisitedList = new List <Visited> [1 << VisitedHashLen];
for (int i = 0; i < VisitedList.Length; i++)
{
VisitedList[i] = new List <Visited>();
}
List <List <int> > keyToChest = new List <List <int> >();
for (int i = 0; i < chests.Count; i++)
{
int k = chests[i].ToOpen;
while (k >= keyToChest.Count)
{
keyToChest.Add(new List <int>());
}
keyToChest[k].Add(i);
}
Visited v = new Visited();
v.Init();
List <int> order = Search(keys, chests, keyToChest, v, 0);
if (order != null)
{
return(string.Join(" ", order));
}
return("IMPOSSIBLE");
}