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  1. import java.util.*;
  2. import java.lang.*;
  3. import java.io.*;
  4.  
  5. class Ideone
  6. {
  7. 	public static long collatz(int maxN)
  8. 	{
  9. 	    long res = 0;
  10. 	    long n = 1;
  11. 	    long count = 0;
  12. 	    long largestCount = 0;
  13. 	    long t = 0;
  14.  
  15. 	    for (long k = 1; k <= maxN; k++)
  16. 	    {
  17. 	        n = k;
  18.  
  19. 	        // reset to zero
  20. 	        count = 0;
  21.  
  22. 			// count how many steps to get to 1
  23. 	        while (n != 1)
  24. 	        {
  25. 	        	// n = collatz(n)
  26. 	            if ((n % 2) == 0)
  27. 	            {
  28. 	                n = n / 2;
  29. 	            }
  30. 	            else
  31. 	            {
  32. 	                n = 3 * n;
  33. 	                n++;
  34. 	            }
  35.  
  36. 	            // count the step
  37. 	            count++;
  38. 	        }
  39.  
  40. 	        // check for maximum count
  41. 	        if (count > largestCount)
  42.             {
  43.                 largestCount = count;
  44.                 res = k;
  45.             }
  46. 	    }
  47.  
  48.  		// log
  49.  		System.out.println("# MAX = "+maxN+", N = "+res+", Steps = "+largestCount);
  50.  
  51. 		// return maximum solution
  52. 	    return res;
  53. 	}
  54.  
  55. 	public static void main (String[] args) throws java.lang.Exception
  56. 	{
  57. 		collatz(20);
  58. 		collatz(50);
  59. 		collatz(100);
  60. 		collatz(1000);
  61. 		collatz(10000);
  62. 		collatz(100000);
  63. //		collatz(1000000);
  64. 	}
  65. }
Time limit exceeded #stdin #stdout 5s 320576KB
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# MAX = 20, N = 18, Steps = 20
# MAX = 50, N = 27, Steps = 111
# MAX = 100, N = 97, Steps = 118
# MAX = 1000, N = 871, Steps = 178
# MAX = 10000, N = 6171, Steps = 261
# MAX = 100000, N = 77031, Steps = 350
https://ideone.com/rZVKFN
language:
Java (HotSpot 12)
created:
8 years ago
visibility:
public

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