private static bool BruteForceRecursion(Board work, ConstraintData data, int Index)
{
if (Index == 81)
return true;
if (work[Index] > 0)
return BruteForceRecursion(work, data, Index + 1);
var loc = new Location(Index);
for (int i = 1; i < 10; i++)
{
if (!data.DigitInRow[i, loc.Row] && !data.DigitInColumn[i, loc.Column] && !data.DigitInZone[i, loc.Zone])
{
work[loc] = i;
data.DigitInRow[i, loc.Row] = data.DigitInColumn[i, loc.Column] = data.DigitInZone[i, loc.Zone] = true;
if (BruteForceRecursion(work, data, Index + 1))
return true;
data.DigitInRow[i, loc.Row] = data.DigitInColumn[i, loc.Column] = data.DigitInZone[i, loc.Zone] = false;
}
}
work[Index] = 0;
return false;
}
private static bool RandomRecursion(Board work, ConstraintData data, List<int> Digits, int Index)
{
if (Index == 81)
return true;
var loc = new Location(Index);
if (work[loc] > 0)
return RandomRecursion(work, data, Digits, Index + 1);
foreach (int test in Digits)
{
if (!data.DigitInRow[test, loc.Row] && !data.DigitInColumn[test, loc.Column] && !data.DigitInZone[test, loc.Zone])
{
work[loc] = test;
data.DigitInRow[test, loc.Row] = data.DigitInColumn[test, loc.Column] = data.DigitInZone[test, loc.Zone] = true;
if (RandomRecursion(work, data, Digits, Index + 1))
return true;
data.DigitInRow[test, loc.Row] = data.DigitInColumn[test, loc.Column] = data.DigitInZone[test, loc.Zone] = false;
}
}
work[loc] = 0;
return false;
}
/// <summary>
/// Returns every digit which may be placed in the calling <see cref="Board"/> instance at the specified <see cref="Location"/>
/// </summary>
/// <param name="Where">The <see cref="Location"/> to check</param>
/// <returns><see cref="List{Int32}"/></returns>
public List<int> Candidates(Location Where)
{
if (_parent[Where] > 0)
return new List<int>();
bool[] present = new bool[10];
foreach (var loc in Where.Blocking)
present[_parent[loc]] = true;
List<int> result = new List<int>();
for (int i = 1; i < 10; i++)
if (!present[i])
result.Add(i);
return result;
}
/// <summary>
/// Attempts to cut 4 locations from the current board, mirrored about both horizontal and vertical axes.
/// </summary>
/// <param name="Stream">An existing <see cref="Random"/> number generator</param>
/// <returns>If the result has a unique solution, then the new <see cref="Board"/>. Otherwise, the original</returns>
public Board Quad(Random Stream)
{
var result = new Board(_parent);
var Filled = _parent.Find.FilledLocations().ToList();
if (Filled.Count > 0)
{
Location loc = new Location(Filled[Stream.Next(Filled.Count)]);
result[loc] = 0;
result[loc.FlipHorizontal()] = 0;
result[loc.FlipVertical()] = 0;
result[loc.FlipHorizontal().FlipVertical()] = 0;
if (result.ExistsUniqueSolution())
return result;
}
return _parent;
}
/// <summary>
/// Determines whether [is same Zone] [the specified <see cref="Location"/> CompareTo].
/// </summary>
/// <param name="CompareTo">The <see cref="Location"/> to be compared.</param>
/// <returns>True or False</returns>
public bool IsSameZone(Location CompareTo)
{
return Zone == CompareTo.Zone;
}
/// <summary>
/// Determines whether [is same row] [the specified <see cref="Location"/> CompareTo].
/// </summary>
/// <param name="CompareTo">The <see cref="Location"/> to be compared.</param>
/// <returns>True or False</returns>
public bool IsSameRow(Location CompareTo)
{
return Row == CompareTo.Row;
}
/// <summary>
/// Determines whether [is same Column] [the specified <see cref="Location"/> CompareTo].
/// </summary>
/// <param name="CompareTo">The <see cref="Location"/> to be compared.</param>
/// <returns>True or False</returns>
public bool IsSameColumn(Location CompareTo)
{
return Column == CompareTo.Column;
}
/// <summary>
/// Determines whether [the specified <see cref="Location"/> CompareTo] is either of the same row, column or zone as the calling instance.
/// </summary>
/// <param name="CompareTo">The <see cref="Location"/> to be compared.</param>
/// <returns>True or False</returns>
public bool IsBlockedBy(Location CompareTo)
{
return (IsSameRow(CompareTo) || IsSameColumn(CompareTo) || IsSameZone(CompareTo));
}
/// <summary>
/// Fills a cell in.
/// </summary>
/// <param name="Where">The <see cref="Location"/> of the cell to fill.</param>
/// <param name="value">The value to place; 0 for clear, or 1-9.</param>
public void PutCell(Location Where, int value)
{
this[Where] = value;
}
/// <summary>
/// Gets the value of a given cell.
/// </summary>
/// <param name="Where">The cell to check; may be provided as either an instance of <see cref="Location"/> or the integer index of the cell.</param>
/// <returns></returns>
public int GetCell(Location Where)
{
return this[Where];
}
/// <summary>
/// Overrides array indexing (suare brackets []) for accessing locations in the Grid.
/// Essentially, it's another way to access GetCell and PutCell.
///
/// You may use
/// <see cref="Location"/> where = new <see cref="Location"/>(x,y);
/// <see cref="int"/> result = myGrid[where];
/// myGrid[where] = result;
/// </summary>
/// <value>
/// The <see cref="int"/> representing the value of the cell (0 for empty, 1-9 for a value).
/// </value>
/// <param name="where">The <see cref="Location"/> to access.</param>
/// <returns></returns>
public int this[Location where]
{
get { return data[where]; }
set { data[where] = value; }
}
/// <summary>
/// Determines whether [the specified <see cref="Location"/> CompareTo] is either of the same row, column or zone as the calling instance.
/// </summary>
/// <param name="CompareTo">The <see cref="Location"/> to be compared.</param>
/// <returns>True or False</returns>
public bool IsBlockedBy(Location CompareTo)
{
return(IsSameRow(CompareTo) || IsSameColumn(CompareTo) || IsSameZone(CompareTo));
}
/// <summary>
/// Determines whether [is same Zone] [the specified <see cref="Location"/> CompareTo].
/// </summary>
/// <param name="CompareTo">The <see cref="Location"/> to be compared.</param>
/// <returns>True or False</returns>
public bool IsSameZone(Location CompareTo)
{
return(Zone == CompareTo.Zone);
}
/// <summary>
/// Determines whether [is same Column] [the specified <see cref="Location"/> CompareTo].
/// </summary>
/// <param name="CompareTo">The <see cref="Location"/> to be compared.</param>
/// <returns>True or False</returns>
public bool IsSameColumn(Location CompareTo)
{
return(Column == CompareTo.Column);
}
/// <summary>
/// Determines whether [is same row] [the specified <see cref="Location"/> CompareTo].
/// </summary>
/// <param name="CompareTo">The <see cref="Location"/> to be compared.</param>
/// <returns>True or False</returns>
public bool IsSameRow(Location CompareTo)
{
return(Row == CompareTo.Row);
}