Character histogram of a string into 64-bit unsigned long.

CharacterHistogram.cs

///
/// CharacterHistogram.cs
/// by tkp
///


void Main()
{
	var s1 = "NOE TIMMY HEATH";
	var s2 = "NOEL TIMOTHY HEATH";
	
	var mash1 = Histogram(s1);
	var mash2 = Histogram(s2);
	var mashhex1 = mash1.ToString("X16"); 
	var mashhex2 = mash2.ToString("X16"); 
	Console.WriteLine("{0} {1} {2}", s1, mashhex1, mash1);
	Console.WriteLine("{0} {1} {2}", s2, mashhex2, mash2);
	var diff = HistogramDiffChars(mash1, mash2);
	
	var mashList1 = s1.Split(new [] {' '}).Select(n => Histogram(n));
	mashList1.Dump();
	diff.Dump();
}

// NOT CURRENTLY USED
public class WordBin
{
	public char Key { get; set; }
	public int BinNum { get; set; }
	public int BinSize { get; set; }
	public int BinOffset { get; set; }
}

// Put character histogram in to 64-bit ULONG
private ulong Histogram(string s)
{
	ulong retval = 0UL;
	var hist = new List<int>(16) {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
	foreach (var c in s.ToLower())
	{
		var i = (int)c;
		var m = i % 16;
		hist[m] += 1;
	}

	hist.Reverse();

	var idx = 0;
	foreach (var v in hist)
	{
		ulong k = (ulong)v << (4*idx++);
		retval += k;
		//Console.WriteLine("{0} {1} {2} {3}", idx, v, k, retval);
	}
	return retval;
}

private int HistogramDiffChars(ulong mash1, ulong mash2)
{
	// Quick check for equality
	if (mash1 == mash2)
	{
		return 0;
	}
	
	int hist1, hist2;
	int dist1 = 0;
	int dist2 = 0;
	
	for (int i = 0; i < 64; i+=4)
	{
		ulong mask = (ulong)15 << i;
		hist1 = (int)((mash1 & mask) >> i);
		hist2 = (int)((mash2 & mask) >> i);
		int diff = Math.Abs(hist1 - hist2);
		if (diff > 0)
		{
			if (hist1 == 0)
			{
				dist2 += diff;
			}
			else if (hist2 == 0)
			{
				dist1 += diff;
			}
			else
			{
				dist1 += diff;
				dist2 += diff;
			}
		}
	}
	return Math.Min(dist1, dist2);
}