private static string FindMaxMergePair(CharInfo ci, int idx, char[] result, StringChar lastSuccessfulChar)
{
if (idx == result.Length)
{
return(new string(result));
}
string s = null;
StringChar lastFailedChar = null;
while (s == null)
{
StringChar sc = ci.RemoveMaxPossibleChar(lastSuccessfulChar, lastFailedChar);
if (sc == null)
{
return(null);
}
result[idx] = sc.c;
s = FindMaxMergePair(ci, idx + 1, result, sc);
if (s == null)
{
lastFailedChar = sc;
ci.AddChar(sc);
}
}
return(s);
}
//public bool CharAvailable(StringChar lastChar)
//{
// return lastChar == null ? true : remainingChars.Count > 0;
//}
public StringChar RemoveMaxPossibleChar(StringChar lastSuccessfulChar, StringChar lastFailedChar)
{
int lastIdx = lastSuccessfulChar != null ? lastSuccessfulChar.idx : -1;
for (char c = 'z'; c >= 'a'; c--)
{
if (!remainingCountsByChar.ContainsKey(c) ||
remainingCountsByChar[c] == 0 ||
(lastFailedChar != null && c >= lastFailedChar.c))
{
// avoid chars that are not part of the word, or are complete, or failed before
continue;
}
if (remainingChars.ContainsKey(c))
{
List <StringChar> indexes = remainingChars[c];
for (int i = 0; i < indexes.Count; i++)
{
StringChar sc = indexes[i];
if (sc.available && sc.idx > lastIdx && sc.idx + remainingCount < s.Length - 1)
{
sc.available = false;
remainingCountsByChar[sc.c]--;
remainingCount--;
return(sc);
}
}
}
}
return(null);
}
private StringChar FindChar(StringChar sc, List <StringChar> lst)
{
for (int i = 0; i < lst.Count; i++)
{
if (lst[i].idx == sc.idx)
{
return(lst[i]);
}
}
return(null);
}
public override bool Equals(object o)
{
if (!(o is StringChar))
{
return(false);
}
StringChar r = (StringChar)o;
return(this.Value.Equals(r.Value));
}
public void AddChar(StringChar sc)
{
if (!remainingChars.ContainsKey(sc.c))
{
remainingChars[sc.c] = new List <StringChar>();
}
StringChar existing = FindChar(sc, remainingChars[sc.c]);
if (existing == null)
{
remainingChars[sc.c].Add(sc);
}
else
{
existing.available = true;
}
if (remainingCountsByChar != null)
{
remainingCountsByChar[sc.c]++;
remainingCount++;
}
}
