Accord.Tests.Math.MatrixTest.nth_element_3 C# (CSharp) Method

        public void nth_element_3()
        {
            // Example from http://www.tenouk.com/cpluscodesnippet/cplusstlvectoralgorithmnth_element.html

            double[] a = { 0, 1, 2, 3, 4, 5, 10, 11, 12, 13, 14, 15, 20, 21, 22, 23, 24, 25 };
            Sort.NthElement(a, 0, a.Length, 3);
            double[] expected = { 0, 1, 2, 3, 4, 5, 10, 11, 12, 13, 14, 15, 20, 21, 22, 23, 24, 25 };
            Assert.IsTrue(a.IsEqual(expected));

            Func<double, double, int> greater = (double elem1, double elem2) =>
            {
                // Less than zero: This instance is less than value.
                // Zero: This instance is equal to value.
                // Greater than zero: This instance is greater than value.
                int ret = -elem1.CompareTo(elem2);
                return ret;
            };

            Sort.NthElement(a, 0, a.Length, 4, greater);
            expected = new double[] { 25, 24, 23, 22, 21, 20, 15, 14, 13, 12, 11, 10, 5, 4, 3, 2, 1, 0 };
            Assert.IsTrue(a.IsEqual(expected));

            Vector.Shuffle(a);
            Sort.NthElement(a, 0, a.Length, 4, greater);
            expected = new double[] { 25, 24, 23, 22, 21, 20, 15, 14, 13, 12, 11, 10, 5, 4, 3, 2, 1, 0 };
            Assert.IsTrue(a.IsEqual(expected));
        }