fannkuch-redux Node.js #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 
*/

function fannkuch(n) {
   const perm1 = [n]   
   for (let i = 0; i < n; i++) perm1[i] = i      
   const perm = [n]
   const count = [n]       
   f = 0, flips = 0, nperm = 0, checksum = 0      
   let 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) {          
            let 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) {
            console.log( checksum )               
            return flips 
         }
         let p0 = perm1[0]
         i = 0
         while (i < r) {
            let 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;      
}
   
let n = (+process.argv.length > 2) 
   ? +process.argv[2] 
   : 7
       
console.log(`Pfannkuchen(${n}) = ${fannkuch(n)}`)

    

NOTES:
64-bit Ubuntu quad core
v23.0.0


 Tue, 22 Oct 2024 22:45:11 GMT

MAKE:
cp -L fannkuchredux.node-8.node fannkuchredux.js

0.21s to complete and log all make actions

COMMAND LINE:
 /opt/src/node-v23.0.0/bin/node fannkuchredux.js 12

PROGRAM OUTPUT:
3968050
Pfannkuchen(12) = 65