/// <summary>
/// Enter the solution to this Cell
/// </summary>
/// <exception cref="ApplicationException">Thrown when all possible solutions have been disqualified</exception>
/// <exception cref="ApplicationException">Thrown when argument has been previously disqualified</exception>
/// <param name="value">Correct value for this Cell</param>
public void Set(char value)
{
// Check whether prior disqualifications have caused an unsolvable situation
if (!Solvable)
{
throw new ApplicationException("This puzzle cannot be solved - all possibilities have been disqualified");
}
// Verify that the specified choice has not itself been disqualified earlier
if (!IsPotentialSolution(value))
{
throw new ApplicationException(string.Format(
"{0} is not valid for this Cell - only {1} allowed",
value,
string.Join(", ", this.RemainingPossibilities)));
}
// Save value as the unique solution for this Cell
CurrentValue = value;
// Disqualify all other choices - once a value is set, nothing else is possible
// (foreach won't work - InvalidOperation is thrown due to changes to collection)
for (int index = RemainingPossibilities.Count - 1; index >= 0; index--)
{
if (RemainingPossibilities[index] != value)
{
RemainingPossibilities.RemoveAt(index);
}
}
}
/// <summary>
/// Determine if a potential solution value is still possible
/// </summary>
/// <exception cref="ArgumentOutOfRangeException">Thrown when argument is too small or too large</exception>
/// <param name="value">Value to check</param>
public bool IsPotentialSolution(char value)
{
// Range validation
if (value < MinValue || value > MaxValue)
{
throw new ArgumentOutOfRangeException("IsPotentialSolution",
string.Format("Argument ({0:d}) must be between {1} and {2}",
value, MinValue, MaxValue));
}
// True if not yet disqualified
return(RemainingPossibilities.Contains(value));
}
/// <summary>
/// Remove a potential solution value from consideration
/// </summary>
/// <exception cref="ArgumentOutOfRangeException">Thrown when argument is too small or too large</exception>
/// <param name="value">Value to exclude from consideration</param>
public void Disqualify(char value)
{
// Range validation
if (value < MinValue || value > MaxValue)
{
throw new ArgumentOutOfRangeException("Disqualify",
string.Format("Argument ({0:d}) must be between {1} and {2}",
value, MinValue, MaxValue));
}
// Remove if value is currently qualified; ignore (benignly) if previously disqualified
if (RemainingPossibilities.Contains(value))
{
RemainingPossibilities.Remove(value);
}
}
