public static void Permute(string source, bool skipZeros, ISet <string> output)
{
// TODO: optimize
//if (PROGRESS) System.out.println("Permute: " + source);
// optimization:
// if zero or one character, just return a set with it
// we check for length < 2 to keep from counting code points all the time
if (source.Length <= 2 && UTF16.CountCodePoint(source) <= 1)
{
output.Add(source);
return;
}
// otherwise iterate through the string, and recursively permute all the other characters
ISet <string> subpermute = new HashSet <string>();
int cp;
for (int i = 0; i < source.Length; i += UTF16.GetCharCount(cp))
{
cp = UTF16.CharAt(source, i);
// optimization:
// if the character is canonical combining class zero,
// don't permute it
if (skipZeros && i != 0 && UCharacter.GetCombiningClass(cp) == 0)
{
//System.out.println("Skipping " + Utility.hex(UTF16.valueOf(source, i)));
continue;
}
// see what the permutations of the characters before and after this one are
subpermute.Clear();
Permute(source.Substring(0, i - 0) // ICU4N: Checked 2nd parameter
+ source.Substring(i + UTF16.GetCharCount(cp)), skipZeros, subpermute); // ICU4N: Substring only has 1 parameter
// prefix this character to all of them
string chStr = UTF16.ValueOf(source, i);
foreach (string s in subpermute)
{
string piece = chStr + s;
//if (PROGRESS) System.out.println(" Piece: " + piece);
output.Add(piece);
}
}
}
