fannkuch-redux Java #8 program

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

   Naive transliteration from Rex Kerr's Scala program
   contributed by Isaac Gouy 
*/

public final class fannkuchredux {
   public static int fannkuch(int n) {
      var perm1 = new int[n];   
      for (int i = 0; i < n; i++) perm1[i] = i;      
      var perm = new int[n];
      var count = new int[n];       
      int f = 0, flips = 0, nperm = 0, checksum = 0;      
      int i, k, r;      
  
      r = n;
      while (r > 0) { 
         i = 0;  
         while (r != 1) { count[r-1] = r; r -= 1; }   
         while (i < n) { perm[i] = perm1[i]; i += 1; }     
        
         // Count flips and update max and checksum
         f = 0;
         k = perm[0];  
         while (k != 0) {
            i = 0;  
            while (2*i < k) {          
               int t = perm[i]; perm[i] = perm[k-i]; perm[k-i] = t;  
               i += 1;           
            }
            k = perm[0];
            f += 1;   
         }         
         if (f > flips) flips = f;         
         if ((nperm & 0x1) == 0) checksum += f; else checksum -= f;
   
         // Use incremental change to generate another permutation   
         var more = true;
         while (more) {   
            if (r == n) {
               System.out.println( checksum );
               return flips; 
            }
            int p0 = perm1[0];
            i = 0;
            while (i < r) {
               int j = i + 1;
               perm1[i] = perm1[j];
               i = j;            
            }
            perm1[r] = p0; 
         
            count[r] -= 1;         
            if (count[r] > 0) more = false; else r += 1;  
         }
         nperm += 1;
      }
      return flips;      
   }
   
   public static void main(String[] args){      
      int n = (args.length > 0) 
         ? Integer.parseInt(args[0]) 
         : 7;
      
      System.out.println("Pfannkuchen("+ n +") = "+fannkuch(n));
   }
}
    

NOTES:
64-bit Ubuntu quad core
java 23 2024-09-17
Java HotSpot(TM) 64-Bit Server VM
(build 23+37-2369, 
mixed mode, sharing)


 Mon, 30 Sep 2024 21:01:01 GMT

MAKE:
mv fannkuchredux.java-8.java fannkuchredux.java
/opt/src/jdk-23/bin/javac -d . -cp .  fannkuchredux.java

2.77s to complete and log all make actions

COMMAND LINE:
 /opt/src/jdk-23/bin/java  -cp . fannkuchredux 12

PROGRAM OUTPUT:
3968050
Pfannkuchen(12) = 65