# fannkuch-redux C# .NET #2 program

## source code

```﻿/* The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/

contributed by Isaac Gouy, transliterated from Mike Pall's Lua program
*/

using System;

class FannkuchRedux
{
public static int[] fannkuch(int n) {
int[] p = new int[n], q = new int[n], s = new int[n];
int sign = 1, maxflips = 0, sum = 0, m = n-1;
for(int i=0; i<n; i++){ p[i] = i; q[i] = i; s[i] = i; }
do {
// Copy and flip.
var q0 = p[0];                                     // Cache 0th element.
if (q0 != 0){
for(int i=1; i<n; i++) q[i] = p[i];             // Work on a copy.
var flips = 1;
do {
var qq = q[q0];
if (qq == 0){                                // ... until 0th element is 0.
sum += sign*flips;
if (flips > maxflips) maxflips = flips;   // New maximum?
break;
}
q[q0] = q0;
if (q0 >= 3){
int i = 1, j = q0 - 1, t;
do { t = q[i]; q[i] = q[j]; q[j] = t; i++; j--; } while (i < j);
}
q0 = qq; flips++;
} while (true);
}
// Permute.
if (sign == 1){
var t = p[1]; p[1] = p[0]; p[0] = t; sign = -1; // Rotate 0<-1.
} else {
var t = p[1]; p[1] = p[2]; p[2] = t; sign = 1;  // Rotate 0<-1 and 0<-1<-2.
for(int i=2; i<n; i++){
var sx = s[i];
if (sx != 0){ s[i] = sx-1; break; }
if (i == m) return new int[]{sum,maxflips};  // Out of permutations.
s[i] = i;
// Rotate 0<-...<-i+1.
t = p[0]; for(int j=0; j<=i; j++){ p[j] = p[j+1]; } p[i+1] = t;
}
}
} while (true);
}

static void Main(string[] args){
int n = (args.Length > 0) ? Int32.Parse(args[0]) : 7;
var pf = fannkuch(n);
Console.Write("{0}\nPfannkuchen({1}) = {2}\n", pf[0], n, pf[1]);
}
}
```

## notes, command-line, and program output

```NOTES:
.NET SDK 8.0.301
Host Version: 8.0.6
Commit: 3b8b000a0e

<OutputType>Exe
<TargetFramework>net8.0
<ImplicitUsings>enable
<Nullable>enable
<AllowUnsafeBlocks>true
<ServerGarbageCollection>true
<ConcurrentGarbageCollection>true
<PublishAot>false
<OptimizationPreference>Speed
<IlcInstructionSet>native

Wed, 29 May 2024 21:17:18 GMT

MAKE:
cp fannkuchredux.csharpcore-2.csharpcore Program.cs
cp Include/csharpcore/program.csproj .
mkdir obj
cp Include/csharpcore/project.assets.json ./obj
~/dotnet/dotnet build -c Release --use-current-runtime
Determining projects to restore...
Restored /home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/program.csproj (in 791 ms).
program -> /home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/bin/Release/net8.0/linux-x64/program.dll

Build succeeded.
0 Warning(s)
0 Error(s)

Time Elapsed 00:00:05.18

6.92s to complete and log all make actions

COMMAND LINE:
./bin/Release/net8.0/linux-x64/program 12

PROGRAM OUTPUT:
3968050
Pfannkuchen(12) = 65
```