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  1. #include <stdio.h>
  2. int collatz(int a1, int *amax)
  3. {
  4.   while (a1 != 1) {
  5.     if (*amax < a1)*amax = a1;
  6.     a1 = (a1 % 2) ?
  7.          a1 * 3 + 1 :
  8.          a1 / 2;
  9.     return 1 + collatz(a1, amax);
  10.   }
  11.   return 1;
  12. }
  13. int main()
  14. {
  15.   int i, amax, len;
  16.   int max_of_i, max_of_amax = 0, max_of_len = 0;
  17.   for (i = 2; i <= 100000; ++i) {
  18.     amax = 0;
  19.     len = collatz(i, &amax);
  20.     if (max_of_amax < amax) {
  21.       max_of_i = i;
  22.       max_of_amax = amax;
  23.       max_of_len = len;
  24.     }
  25.     // printf("%d %d %d\n", i, len, amax);
  26.   }
  27.   printf("%d %d %d\n", max_of_i, max_of_len, max_of_amax);
  28.   return 0;
  29. }
  30.  
Success #stdin #stdout 0.05s 2292KB
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stdin 
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stdout 
77671 232 1570824736
https://ideone.com/RbjPO8
language:
C (gcc 8.3)
created:
10 years ago
visibility:
secret

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