Add missing RandomShuffle to Combinatorics about mathnet-numerics HOT 2 CLOSED

    /// <summary>
    /// Creates a Random Permutation of lenght len (indexes 0 to len -1). Internally uses System.Random with the same seed.
    /// using RandomPermutation(int len, AbstractRandomNumberGenerator rnd) can give better randomness.
    /// </summary>
    /// <param name="len">the length of the Permuation</param>
    /// <returns></returns>
    public static Permutation RandomPermutation(int len)
    {

        int[] keys = new int[len];
        int[] items = new int[len];

        for (int i = 0; i < keys.Length; i++)
        {
            items[i] = i;
            lock (SortingExtensions.random)//System Random is not thread save!
            {
                keys[i] = SortingExtensions.random.Next();
            }
        }
        Sorting.Sort(keys, items);
        //although not neccessary here, the inverse of a Permutation corrseponds to a given sort order, if that Permuation was to be used to sort a matrix in the same order as the List.
        return new Permutation(items).Inverse();
    }

    /// <summary>
    /// Creates a Random Permutation of lenght len (indexes 0 to len -1) using a supplied random Number Generator
    /// </summary>
    /// <param name="len">the lenght of the permuation</param>
    /// <param name="rnd">The Random number Generator</param>
    /// <returns>The requested Permutation</returns>
    public static Permutation RandomPermutation(int len, AbstractRandomNumberGenerator rnd)
    {

        int[] keys = new int[len];
        int[] items = new int[len];

        for (int i = 0; i < keys.Length; i++)
        {
            items[i] = i;
            keys[i] = rnd.Next();
        }
        Sorting.Sort(keys, items);

        // The inverse of a Permutation corrseponds to a given sort order, 
        // if that Permuation were to be used to sort a matrix in the same order as the random List above.
        // Although it is neccessary here , since we are generating a random Permuation,
        // for consistancy the Permuation is also inversed. 
        return new Permutation(items).Inverse();
    }
}