public bool AddQueen(QueenItem queenItem)
{
MarkRowVisited(queenItem.Row);
MarkColVisited(queenItem.Col);
MarkDiagonalLeftUpVisited(queenItem.Row, queenItem.Col);
MarkDiagonalRightUpVisited(queenItem.Row, queenItem.Col);
MarkDiagonalLeftDownVisited(queenItem.Row, queenItem.Col);
MarkDiagonalRightDownVisited(queenItem.Row, queenItem.Col);
QueenList.Add(queenItem);
return(true);
}
public static int GetNQueens(int n)
{
var result = new List <List <QueenItem> >();
int min = Int32.MinValue;
for (int i = 0; i < n; i++)
{
var current = new QueenItem(i, 0, n - 1, n - 1);
current.AddQueen(current);
Queue <QueenItem> queue = new Queue <QueenItem>();
queue.Enqueue(current);
while (queue.Count > 0)
{
var currentItem = queue.Dequeue();
if (currentItem.Size == min)
{
result.Add(currentItem.QueenList);
}
if (currentItem.Size > min)
{
result = new List <List <QueenItem> >
{
currentItem.QueenList
};
min = currentItem.Size;
}
if (currentItem.Col + 1 < n)
{
for (int j = 0; j < n; j++)
{
if (currentItem.IsSafe(j, currentItem.Col + 1))
{
var newItem = new QueenItem(j, currentItem.Col + 1, n - 1, n - 1);
currentItem.QueenList.ForEach(item => newItem.AddQueen(item));
newItem.AddQueen(newItem);
queue.Enqueue(newItem);
}
}
}
}
}
return(min == n ? result.Count : 0);
}