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  1. #include <stdio.h>
  2.  
  3. int collatz(int a1, int *amax)
  4. {
  5. int count;
  6.  
  7. count = 1;
  8. *amax = a1;
  9. for(;;) {
  10.   if (a1 == 1) {
  11.     break;
  12.   }
  13.   count++;
  14.   if (a1 % 2 == 0) {
  15.     a1 /= 2;
  16.   } else {
  17.     a1 = a1 * 3 + 1;
  18.   }
  19.   if (a1 > *amax) {
  20.     *amax = a1;
  21.   }
  22. }
  23. return count;
  24. }
  25.  
  26. int main()
  27. {
  28. int i;
  29. int amax;
  30. int maxlen;
  31. int maxini;
  32. int len;
  33.  
  34. maxlen = 0;
  35. maxini = 0;
  36. for (i = 2; i <= 100000; i++) {
  37.   len = collatz(i, &amax);
  38.   if (len > maxlen) {
  39.     maxlen = len;
  40.     maxini = i;
  41.   }
  42. }
  43. printf("%d, %d\n", maxini, maxlen);
  44. return 0;
  45. }
  46.  
Success #stdin #stdout 0.04s 2248KB
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77031, 351
https://ideone.com/rYkh0s
language:
C (gcc 8.3)
created:
11 years ago
visibility:
public

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