BinCoeffBase BCB; // Holds ref to actual binomial coeff class - Bincoeff (uint), BinCoeffL (ulong), or BinCoeffBigInt (BigInteger).
//
public BinCoeffGen(int numItems, int groupSize, bool initTable = false)
{
// This constructor builds the index tables used to retrieve the index to the binomial coefficient table.
// n is the number of items and k is the number of items in a group, and reflects the case n choose k.
//
// Get the total number of unique combinations.
BigInteger totalCombos = BinCoeffBase.GetCombosCountBigInt(numItems, groupSize);
// If n & k result in overflow of ulong, then use BigInteger. Otherwise either use int or long for best performance.
if (totalCombos > ulong.MaxValue)
{
BCB = new BinCoeffBigInt(numItems, groupSize, totalCombos);
}
else if (totalCombos <= int.MaxValue)
{
BCB = new BinCoeff <T>(numItems, groupSize, (uint)totalCombos, initTable);
}
else
{
BCB = new BinCoeffL(numItems, groupSize, (ulong)totalCombos);
}
}
public static void OutputCombos <U>(string filePath, string[] dispChars, string sep, string groupSep, int maxCharsInLine,
BinCoeffBase bcb, U startRank, U endRank)
{
// This function writes out the K indexes in sorted order to either a file or a list. It is used by all 3 implementations.
// U specifies uint, ulong, or BigInteger.
// filePath - path & name of file.
// dispChars - if not null, then the string in DispChars is displayed instead of the
// numeric value of the corresponding combination.
// sep - String used to separate each individual combination in a group.
// groupSep - String used to separate each combination group.
// maxCharsInLine - maximum number of chars in an output line.
// bcb - the type to be worked on - either Bincoeff (uint), BincoeffL (ulong), or BinCoeffBig (BigInteger).
// startRank - the first combo that should be output. Range is zero to NumCombos - 1.
// endRank - the last combo that should be output. If startRank > endRank, then output is in descending order.
//
// No more than 2^31 combinations are output.
//
const int bufferSize = 65536;
int loop1, n, outPos = 0;
int offset = 0, inc, outCount = 0, elemCount = 0;
int maxCharsInN = bcb.NumItems / 10 + 1;
var kIndexes = new int[bcb.GroupSize];
var outbuf = new byte[maxCharsInLine + 2];
string s, s1;
StringBuilder sb = new StringBuilder();
FileStream outFile = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None, bufferSize, FileOptions.None);
// Set to output in ascending or descending order depending if startRank < endRank.
dynamic dynStart = startRank, dynEnd = endRank;
inc = (dynStart > dynEnd) ? -1 : 1;
outCount = (dynEnd - dynStart) * inc;
// Output the K Indexes
do
{
bcb.GetCombFromRank(startRank, offset, kIndexes);
offset += inc;
for (loop1 = 0; loop1 < bcb.GroupSize; loop1++)
{
n = kIndexes[loop1];
if (dispChars != null)
{
s = dispChars[n];
}
else
{
s1 = "{0, " + maxCharsInN.ToString() + "}";
s = String.Format(s1, kIndexes[loop1]);
}
sb.Append(s);
if (loop1 < bcb.GroupSizeM1)
{
sb.Append(sep);
}
}
if (outPos + sb.Length >= maxCharsInLine)
{
outbuf[outPos++ - groupSep.Length] = (byte)'\r';
outbuf[outPos - groupSep.Length] = (byte)'\n';
outFile.Write(outbuf, 0, outPos - groupSep.Length);
outPos = 0;
}
sb.Append(groupSep);
// Move the string value to the output buffer.
for (loop1 = 0; loop1 < sb.Length; loop1++)
{
outbuf[outPos++] = (byte)sb[loop1];
}
sb.Remove(0, sb.Length);
elemCount++;
} while (elemCount <= outCount);
if (outPos > 0)
{
outFile.Write(outbuf, 0, outPos - groupSep.Length);
}
outFile.Close();
outFile.Dispose();
}