Determinant and permanent: Difference between revisions
Add C# implementation
(added RPL) |
(Add C# implementation) |
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return 0;
}</syntaxhighlight>
=={{header|C#}}==
{{trans|Go}}
<syntaxhighlight lang="C#">
using System;
using System.Collections.Generic;
using System.Linq; // This is required for LINQ extension methods
class Program
{
static IEnumerable<IEnumerable<int>> GetPermutations(IEnumerable<int> list, int length)
{
if (length == 1) return list.Select(t => new int[] { t });
return GetPermutations(list, length - 1)
.SelectMany(t => list.Where(e => !t.Contains(e)),
(t1, t2) => t1.Concat(new int[] { t2 }));
}
static double Determinant(double[][] m)
{
double d = 0;
var p = new List<int>();
for (int i = 0; i < m.Length; i++)
{
p.Add(i);
}
var permutations = GetPermutations(p, p.Count);
foreach (var perm in permutations)
{
double pr = 1;
int sign = Math.Sign(GetPermutationSign(perm.ToList()));
for (int i = 0; i < perm.Count(); i++)
{
pr *= m[i][perm.ElementAt(i)];
}
d += sign * pr;
}
return d;
}
static int GetPermutationSign(IList<int> perm)
{
int inversions = 0;
for (int i = 0; i < perm.Count; i++)
for (int j = i + 1; j < perm.Count; j++)
if (perm[i] > perm[j])
inversions++;
return inversions % 2 == 0 ? 1 : -1;
}
static double Permanent(double[][] m)
{
double d = 0;
var p = new List<int>();
for (int i = 0; i < m.Length; i++)
{
p.Add(i);
}
var permutations = GetPermutations(p, p.Count);
foreach (var perm in permutations)
{
double pr = 1;
for (int i = 0; i < perm.Count(); i++)
{
pr *= m[i][perm.ElementAt(i)];
}
d += pr;
}
return d;
}
static void Main(string[] args)
{
double[][] m2 = new double[][] {
new double[] { 1, 2 },
new double[] { 3, 4 }
};
double[][] m3 = new double[][] {
new double[] { 2, 9, 4 },
new double[] { 7, 5, 3 },
new double[] { 6, 1, 8 }
};
Console.WriteLine($"{Determinant(m2)}, {Permanent(m2)}");
Console.WriteLine($"{Determinant(m3)}, {Permanent(m3)}");
}
}
</syntaxhighlight>
{{out}}
<pre>
-2, 10
-360, 900
</pre>
=={{header|C++}}==
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