Improved Combinations with the BigInteger Data Type: Listing 3.

Successor method to return next combination.

public Combination Successor()
{
  if (this.data.Length == 0 ||
    this.data[0] == this.n - this.k)
    return null;

  Combination result = new Combination(this.n, this.k);

  int i;
  for (i = 0; i < this.k; ++i)
    result.data[i] = this.data[i];

  i = this.k - 1;
  while (i > 0 && result.data[i] == this.n - this.k + i)
    --i;

  ++result.data[i];

  for (int j = i; j < this.k - 1; ++j)
    result.data[j + 1] = result.data[j] + 1;

  return result;
}

About the Author

Dr. James McCaffrey works for Microsoft Research in Redmond, Wash. He has worked on several Microsoft products including Azure and Bing. James can be reached at [email protected].

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