source code
    
    
/* The Computer Language Benchmarks Game
   https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
   Naive transliteration from bearophile's program
   contributed by Isaac Gouy 
*/
import Foundation
func seq_lines() -> [String] {
   while let line = readLine() {   
      if (line.hasPrefix(">THREE")) { break }     
   }  
   var lines: [String] = []
   while let line = readLine() {   
      if (line.hasPrefix(">")) { break }   
      lines.append(line)
   } 
   return lines
}
func base_counts(_ bases: Int, _ seq: String.UTF8View) -> [String: Int] {
   var counts: [String: Int] = [:]
   let size = seq.count + 1 - bases  
   var i = 0
   while i < size {
      let start_offset = seq.index( seq.startIndex, offsetBy: i)
      let end = seq.index( start_offset, offsetBy: bases)         
      if let nucleo = String( seq[start_offset..<end] ) {
         if let v = counts[nucleo] {   
            counts[nucleo] = v + 1  
         } else {
            counts[nucleo] = 1 
         }
      } 
      i += 1      
   }
   return counts   
}
func sorted_freq(_ bases: Int, _ seq: String.UTF8View) -> [(String, Double)] {
   let kv_ = base_counts(bases, seq)
   let size = Double(seq.count + 1 - bases)  
   let sorted_ = kv_.sorted{ $1.1 < $0.1 }
   return sorted_.map{ ($0.0, 100.0 * Double($0.1) / size) }
}
func specific_count(_ code: String, _ seq: String.UTF8View) -> Int {  
    return base_counts(code.count, seq)[code] ?? 0 
}    
func main() {
   let lines = seq_lines()
   let seq = lines.map{$0.uppercased()}.joined().utf8
  
   for base in [1,2] {
      for (k,v) in sorted_freq(base, seq) {   
         print( k, String(format: "%.3f", v))          
      }
      print()      
   }
   
   for code in ["GGT", "GGTA", "GGTATT",
         "GGTATTTTAATT", "GGTATTTTAATTTATAGT"] {    
      print("\(specific_count(code, seq))\t\(code)")         
   }
}
main()
    
  
  
    
      
notes, command-line, and program output
    
    
NOTES:
64-bit Ubuntu quad core
Swift version 6.0.3
(swift-6.0.3-RELEASE)
Target: x86_64-unknown-linux-gnu
 Sun, 23 Feb 2025 00:46:36 GMT
MAKE:
/opt/src/swift-6.0.3-RELEASE/usr/bin/swiftc knucleotide.swift-8.swift -Ounchecked -wmo  -o knucleotide.swift-8.swift_run
14.46 seconds to complete and log all make actions
COMMAND LINE:
 ./knucleotide.swift-8.swift_run 0 < knucleotide-input25000000.txt
PROGRAM OUTPUT:
A 30.295
T 30.151
C 19.800
G 19.754
AA 9.177
TA 9.132
AT 9.131
TT 9.091
CA 6.002
AC 6.001
AG 5.987
GA 5.984
CT 5.971
TC 5.971
GT 5.957
TG 5.956
CC 3.917
GC 3.911
CG 3.909
GG 3.902
1471758	GGT
446535	GGTA
47336	GGTATT
893	GGTATTTTAATT
893	GGTATTTTAATTTATAGT