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  1. import java.util.ArrayList;
  2. import java.util.Random;
  3. import java.util.concurrent.Callable;
  4. import java.util.concurrent.ExecutorService;
  5. import java.util.concurrent.Executors;
  6. import java.util.concurrent.ThreadFactory;
  7.  
  8. class SeedFinder {
  9.  
  10.   static class SearchTask implements Callable<Long> {
  11.  
  12.     private final char[] goal;
  13.     private final long start, step;
  14.  
  15.     public SearchTask(final String goal, final long offset, final long step) {
  16.       final char[] goalAsArray = goal.toCharArray();
  17.       this.goal = new char[goalAsArray.length + 1];
  18.       System.arraycopy(goalAsArray, 0, this.goal, 0, goalAsArray.length);
  19.       this.start = Long.MIN_VALUE + offset;
  20.       this.step = step;
  21.     }
  22.  
  23.     @Override
  24.     public Long call() throws Exception {
  25.       final long LIMIT = Long.MAX_VALUE - this.step;
  26.       final Random random = new Random();
  27.       int position, rnd;
  28.       long seed = this.start;
  29.  
  30.       while ((Thread.interrupted() == false) && (seed < LIMIT)) {
  31.         random.setSeed(seed);
  32.         position = 0;
  33.         rnd = random.nextInt(27);
  34.         while (((rnd == 0) && (this.goal[position] == 0))
  35.                 || ((char) ('`' + rnd) == this.goal[position])) {
  36.           ++position;
  37.           if (position == this.goal.length) {
  38.             return seed;
  39.           }
  40.           rnd = random.nextInt(27);
  41.         }
  42.         seed += this.step;
  43.       }
  44.  
  45.       throw new Exception("No match found");
  46.     }
  47.   }
  48.  
  49.   public static void main(String[] args) {
  50.     final String GOAL = "hello".toLowerCase();
  51.     final int NUM_CORES = Runtime.getRuntime().availableProcessors();
  52.  
  53.     final ArrayList<SearchTask> tasks = new ArrayList<>(NUM_CORES);
  54.     for (int i = 0; i < NUM_CORES; ++i) {
  55.       tasks.add(new SearchTask(GOAL, i, NUM_CORES));
  56.     }
  57.  
  58.     final ExecutorService executor = Executors.newFixedThreadPool(NUM_CORES, new ThreadFactory() {
  59.  
  60.       @Override
  61.       public Thread newThread(Runnable r) {
  62.         final Thread result = new Thread(r);
  63.         result.setPriority(Thread.MIN_PRIORITY);
  64.         result.setDaemon(false);
  65.         return result;
  66.       }
  67.     });
  68.     try {
  69.       final Long result = executor.invokeAny(tasks);
  70.       System.out.println("Seed for \"" + GOAL + "\" found: " + result);
  71.     } catch (Exception ex) {
  72.       System.err.println("Calculation failed: " + ex);
  73.     } finally {
  74.       executor.shutdownNow();
  75.     }
  76.   }
  77. }
  78.  
Time limit exceeded #stdin #stdout 5s 381632KB
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https://ideone.com/ROhmTA
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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