Method NQueens

csharp/Backtracking/NQueens.cs:5–10

(int n)

    int res = 0;

    public int NQueens(int n)
    {
        dfs(0, new HashSet<int>(), new HashSet<int>(), new HashSet<int>(), n);

        return res;
    }

    private void dfs(int r, ISet<int> diagonalsSet, ISet<int> antiDiagonalsSet, ISet<int> colsSet, int n)
    {