public static PuzzleTreeNode ParseGarbage(string stream, ref int index)
{
if (stream[index] != '<')
{
throw new InvalidStreamException(InvalidStreamMessage.MissingGarbageStart);
}
index++;
var treeNode = new PuzzleTreeNode(0); // garbage has no score
while (index < stream.Length)
{
if (stream[index] == '!')
{
index += 1; // increment index so that next character is skipped.
}
else if (stream[index] == '>')
{
index++;
return(treeNode);
}
index++;
}
throw new InvalidStreamException(InvalidStreamMessage.MissingGarbageEnding);
}
public static int ComputeScore(PuzzleTreeNode treeNode)
{
int score = treeNode.Score;
foreach (var child in treeNode.Children)
{
score += ComputeScore(child);
}
return(score);
}
public static PuzzleTreeNode ParseGroup(string stream, ref int index, int score)
{
if (stream.Trim().Length == 0 || stream[index] != '{')
{
throw new InvalidStreamException(InvalidStreamMessage.MissingGroupStart);
}
int startIndex = index;
index++;
var treeNode = new PuzzleTreeNode(score);
bool commaIsAppropriate = false;
while (index < stream.Length)
{
if (stream[index] == '<' && !commaIsAppropriate)
{
var garbageNode = ParseGarbage(stream, ref index);
treeNode.Children.Add(garbageNode);
commaIsAppropriate = true;
}
else if (stream[index] == '{' && !commaIsAppropriate)
{
var groupNode = ParseGroup(stream, ref index, score + 1); // recursively call ParseGroup()
commaIsAppropriate = true;
treeNode.Children.Add(groupNode);
}
else if (stream[index] == '}')
{
treeNode.Stream = stream.Substring(startIndex, index - startIndex);
index++;
return(treeNode); // end recursive call
}
else if (stream[index] == ',' && commaIsAppropriate)
{
index++;
commaIsAppropriate = false;
}
else
{
throw new InvalidStreamException(InvalidStreamMessage.InvalidGroupCharacter);
}
}
throw new InvalidStreamException(InvalidStreamMessage.MissingGroupEnding);
}
